I'd like to suggest at least putting an STS on your bow to help prevent so much shock in the limbs, plus you could then take off any and all string silencers, which would help gain a few fps! I think the STS would be a big help in preventing limb damage in your case!
I've got a good friend who is a speed freak. He is shooting his Mathews SB with very lite arrows and is well over 300 fps! I can't remember exactly, but his arrows are way under the recommended 5 gr./# of pull!