If you were to use a 25'6" mast section and a slightly shorter boom and dont try for "140 sq ft" of sail area (remember that half the diameter of the mast bounded by the luff length of the sail is counted as sail area, and it is) you should end up with an actual sail area (minus the mast area) of about 130 to 135 sq ft. That is more than enough on a 14' cat with that aspec ration for the main sail, any more on the main and the boat becomes very "condition specific" losing out on conditions other than its "ideal", the "actual sail area" of an "A" class main sail is only a few sq ft more!! And only use about 6" of aft mast rake at the head of the mast, if the boat is balanced that should be all that is required (forget about Hobie 14 and similar, they have a sail plan that is basically unbalanced and use extreme aft rake to try to correct other inefficiencies in their design). When you have the sail plan worked out and scaled onto the plan, then position the C/B position to suit the C of E of the sail, not visa versa. It is not critical how far back the C/B's are positioned aft (with in reason) the only real effect is that the further aft the boards are the higher the boat will sail to windward - Take a look at where the mast and C/B's are on the last few "C" class cats - their rigs and C/Boards are as far back as it is possible to put them and they seem to perform fairly well!!
Darryl