cottonfarmer,
Not to second guess you, but your speed and KE sound kind of low for 65lbs of pull and 28" draw. Are you sure those numbers are correct?

If you are indeed getting only 47 ft-lbs of KE, I wouldn' t shoot mechs. At 240 fps, you should be able to get fixed heads to fly perfectly and you' ll get better penetration. If you find that your KE is higher, you could probably use one of the smaller cut mechs. The size of the mech must match your KE level or you won' t get good performance.

Good luck.