Rich, I just got setup to shoot alittle F-Class myself. I bought myself an Edgewood Original, it weighs about 10 pounds full of blacksand.
I was shooting the same rest you have. But another shooter kept telling me about the new Caldwell Firecontrol. I told him to bring it to the next match, well to shorten the story I now own his rest /ubbthreads/images/graemlins/smile.gif
I'm shooting the 6 Dasher for F-Class. So far I have tried 105 A-Max, 105 Lapua, 107SMK, 105 Berger VLD, 108 Berger Match BT. They all shoot acceptable, but both of the Bergers shoot smaller than everything which comes to no suprise.
I have shot the 108's and 105's in the same match in the same conditions. It seems that the 105's give me more X's.