I don't think that moving from 125 to 185 will increase FOC all that much. You may want to looking into steel adapters and glue on heads.

But, here is my main caution. Aluminums do not fly all that well with extreme FOC. Personally, I could not get my aluminums to fly that great past about a 150 grain head. Iasked the question to Dr. Ashby himself and he found the same results with aluminum. With carbon though, I was able to get 26% FOC and had great flight. I was using 190 grain glue ons, adapter and brass insert. I also had 5 grain per inch tubes which made a 720 grain arrow.