I haven't found any binding problems with cylindrical hammers.... unless they are too tight in the tube, of course.... I would only reduce the center diameter to save weight.... and if you are using a PRod trigger, remember that won't work.... the sear has to be hold down all the time except when cocked....Bob
Thread on hammer and travel combinations you might find helpful.... http://www.gatewaytoairguns.org/GTA/index.php?topic=99949.0Using that formula, you should be able to stay to less than about 20 lbs. cocking force.... Bob
Remember, once you get to a certain point, more hammer strike will not add any velocity, just waste air.... FPE is a combination of barrel length, caliber and pressure.... assuming free flowing ports, of course.... Bob