Back drag is the fallout of the strength of the Pawl springs, and the friction of the "bearing" surfaces the driver head has both round and flat on the plates of cavity surfaces.
Getting those surfaces as smooth as possible may help and many have trimmed springs for overly strong springs. take one of your existing rats apart that is particularly bad ad clean it, then lightly lube it, and see where that gets you.
If it still needs improvement, smooth those surfaces, and if they are already smooth, use some old fashioned Clover Valve Lapping Compond to smooth them further, then attack the springs, SLOWLY.