I want to start getting some prices from various lofts on the cost of sails- especially the mainsail, as this will be the most similar sail on every boat.

First- Boom or Boomless? Most racing boats go with booms for the added tuning ability. The Mysteres are running boomless and don't seem to mind at all. I personally prefer a boomless sail, with a stiff lower batten and an inhaul from the tack to the clew to adjust the flatness/fullness of the sail.

Second (because it is dependant on the condition above)-with a 24' mast, how long can the luff of the sail be?

Third- how long should the foot of the sail be? Mostly, this depends on the location of the mast beam- but with a boom, the sail could extend past the aft beam.