What ft/lb would be considered safely legal to set a springer?

[Dave2345678]

I normally set springers to a max of 10.5 - 10.8 with the most efficient pellet.
I check ME in summer and winter and adjust accordingly

The problem is, whilst most models may seem nicer to shoot at 10.5 typically and thats fine, but Ive been out with an FAC registered pal using a Rapid and a Patriot (both legally running 20 ish) and the difference on game was night and day.
Even shot placement became less critical. Completely broken skulls on Squirrel. Less than ideal body shots, ripped clean through and didnt seem any lesser for not having been ideally shot.
The energy given up thing in regard of not passing through seemed mute.
Both sides of the shoulders done at 30 yards, which at 10.5 would have been a bad hit.
It has to be better to have that availability for the private game shooter, then having the choice to go up in pellet weight/slug if you dont wish the pass through.
Legitamate hunter/land owner gets choice. FT a 12 limit.