I have a sol Cat 18 and I am sure that the mail sail is not attached to the boom correctly. Their appears to be travler on the boom but no connections to the main sail and the main sail is just tied to the boom to an eyelet on the side of the boom. I don't know what everything is called. If anyone has any photos or a manual on how to connect the main to the boom it would be great.
in light air.. you want a full (rounder) sail shape. this will give you more power.
in heavy air you want a flat shape. this will make the air slide off the sail faster, creating less power (you want less power in 20+mph wind).
the same for the jib, and even your rigging (fore and side stays). the tighter she blows, the tighter your rigging/sheeting goes.
your out and downhaul are micro-tuners.. your jib and main sheet are the main tuners. in heavy air it is better to let out the travler than the main to depower as letting out the mainsheet will allow the mainsail to get fuller(round) and create more power. In heavy air i let the travler out 3-6 inches to keep me from capsizing.
With the Solcat, and perhaps all loose-footed mainsails, you must use the outhaul to flatten the sail. If your outhaul is loose, no amount of mainsheet traveler will flatten the sail. The reason for this (at least with the Solcat) is in the placement of the boom car to which the clew attaches. Tightening the outhaul pulls the car towards the end of the boom, loosening it allows it to move towards the mast. When the outhaul is loose, and the mainsheet is pulled very tight, the clew of the sail is actually pushed towards the mast, creating substantial draft in the sail. Allowing the mainsheet's traveler to move won't change the draft created as the boom is pulled down by the mainsheet.
This isn't contrary to what you said, it is in addition! When the wind's really blowing, I have to tighten the outhaul, downhaul, *and* let the traveler go. But from experience, the traveler didn't do much at all without the outhaul.
Another finicky adjustment (that might be particular to my solcat) is the downhaul. Once I've set it I can't loosen it easily. The rotation of the mast creates friction on the bolt rope, which holds the setting until I tack, jibe, or manually rotate the mast to relieve some friction.