Decide on a sail maker sail.

If I choose a couple of standard (common dinghies) sails. Can the sail maker
(dealer) tell
1. how large mast bending it's designed for (his standard CAD pattern for
that dinghy)?
2. if it's a weak or strong wind sail?

3. Is it usually possible to choose the sails reef technique and /or
fastening method?

4. Can a tube GRP mast match an aluminum one in matter of stiffness? ...or
will it get way to big radius to match?

Morgan O.