Hi JB..I'd go 19 ft lbs as the sweet spot. Anything more is a little too much. Slight off thread but on FAC power levels I remember shooting a Webley Venom 97 running at 16.8 ft lbs it was unreal..a mild nudge in the shoulder like a legal limit rifle..it was .22 but really nice at that power level.
Mach 1.5