Because every adjustment affects several others, it will take several rounds of changes to reach optimum performance. There have been several builders of this boat, so there is no valid starting point.
Rig tension: fairly tight. 250 lbs shroud tension is a good place to start.
Mast rake: start with less than 2 deg, but recognize that this will most likely be changed after other adjustments.
For keel stepped masts, start by blocking the mast at the partners in its neutral position after the rig is tensioned (i.e. apply no block-induced prebend). If the main then seems a bit full in the lower half while sailing, perhaps shown by too much "backwinding" in the jib overlap region (after the jib is properly tuned), then induce prebend by putting a 3/4 inch block behind the mast.
Mainsail:
The Benson main is designed with the shape all built into the sail, and the luff cut to fit the mast specified in your order. It should assume its optimum shape in medium wind with very little tension on any of the control lines. Sails from other makers are typically too full in the lower half and need a lot of outhaul tension and perhaps some mast blocking and vang (for mast bend) to pull them flatter. With your new Benson sail, you should always start with control lines eased.
The guide below is for the Benson main in medium wind.
Halyard/ cunningham: raise sail to full height, but do not stretch the luff. If you see any hint of a crease parallel to the mast, then ease controls immediately or you may damage the sail. While the sail is new, use the cunningham only to smooth out slight horizontal wrinkles along the luff. The highly stable finish on the sailcloth prevents much movement of the draft position, either by the wind pressure or by the cunningham. After the sail has aged and the cloth is softer, then the Cunningham may become useful for moving the draft forward.
Outhaul: upwind the shelf foot should be just fully open. Tension the outhaul until the center of the sail foot just starts to be pulled towards the boom, and then ease it slightly.
Vang: should not be tight in medium air. Mainsheet: pull in the mainsheet until the upper leech telltale stalls occasionally. The lower leech telltale(s) should always stream.
Jib: Sails with a hard racing finish are damaged by folding or creasing. Never allow a roller furled sail to bend while hoisting or dropping sail. Raise the sail unfurled, then roll it up. Unroll the sail before releasing the halyard. For storage, always roll parallel to the horizontal seams; avoid bending the roll.
Start with the fairleads near the center of the tracks. Adjust the sheet so that the area near the clew is parallel to the boat centerline. This means that the air will be exiting the bottom of the sail straight aft. Now look up at the slot. The rest of the sail should twist off to leave a fairly open slot between the leech and the mainsail. You should be able to visualize the air leaving the jib and flowing smoothly over the main. If the slot is too small, move the fairlead aft, readjust the sheet as above (clew area parallel to centerline) and look again at the slot. If the slot is too open, move the fairlead forward. Repeat several times. If you have been fast in the past, judge the slot by the end of the spreaders as before. A decent place to start is just outside the tips of 15 inch spreaders. Now note the jib telltales as the boat is slowly turned to windward. It is acceptable either that all of the windward telltales start to flutter at the same time, or that the top one flutters slightly before the others. If the top one flutters after any of the others, move the fairlead aft to open up the slot.
If you are pointing high, but seem a bit slow, you can try easing the jib halyard slightly to get more curvature in the jib luff using forestay sag. Often it is better to just ease the jib sheet and foot slightly.
The luff cloth tension has been preset at the loft using the lashing at the head. It usually need not be changed during the first season of sailing. Older sails may benefit from readjustment to restore the draft position. Use of a jib cunningham on the new sail is usually ineffective (because of the highly stabilized cloth), and is not recommended.
On the water: Now sail to windward with minimum heel. Check the position of the tiller; it should be 2 to 4 degrees to windward (forward end about 3 inches up from centerline). If this is not correct, you must change the mast rake and start completely over. Neutral or lee helm is corrected by raking the mast aft; excess weather helm is corrected by removing rake. Change the rake by adjusting the shrouds at the chainplates; shorten to rake, lengthen to remove rake. Reset the mast blocks. The other adjustment most affected by changing the rake is the jib fairlead position. More rake will require that the lead be moved forward and vice versa. Still you must go through the rest of the tuning procedure to determine the amount. Once the boat is in balance with the small weather helm, it will be a pleasure to sail. Note that weather helm is strongly affected by heel, so try to sail quite flat.
Very light wind: ease the mainsheet so the end of the boom is over the rail. Sit to leeward and heel the boat until the rail is quite near the water. Hold the jib clew in hand and try and keep the slot open.
Heavy wind: On windy days it is often useful to start with a flattened main by inducing mast prebend with a block at the partners (keel stepped mast). If the wind lessens, you will need to remove that block to get back up to speed. Try to keep the boat flat by hiking hard. As this becomes impossible, try these in the following order: tighten the outhaul, tighten the vang to bend the mast (both flatten the main; you may need to use the cunningham to move the draft forward, but do this very carefully). Ease the traveler if one is installed. Ease the mainsheet early in puffs before heel gets excessive (anticipate).
Reaching without spinnaker: Trim the jib to keep all telltales streaming. For a broader reach the leeward telltales should be at the edge of stalling.
Trim the main to keep the leech telltales streaming. Use the vang to minimize twist. Check for correct twist by pulling in the sheet (or bearing off) and checking whether the upper telltale stalls at the same time as the middle one. If it stalls later, tighten the vang, or vice versa. The outhaul can be eased to increase camber, but remember to retension it for the next upwind leg. You will lose much more distance by forgetting to reset it for the beat than you will lose by failing to ease it for the reach. For a broader reach, trim the sheet so that the leech telltales are at the edge of stalling but still streaming consistently.