I think you're quite right Martin-but there must be a point somewhere where the excess weight starts to slow the engine. I suppose if one was anal, had a lathe, plenty of brass and a lot of spare time, one could machine up a whole raft of heavy spinners, in increments of say half an ounce difference, and then, with all other elements-fuel, prop, temp, etc constant, run a series of tests..........

ChrisM
'ffkiwi'