Colorado - I think you are correct about the extra recoil surmise on T-7 with the heaviest load you used.
: That double of yours with 150gr. of powder will do just fine for all big game hunting in the US and Canada. the normal 'light' load for the 12 bore ctg. guns for Africa was 150gr. (or maybe 151gr.) My 12 bore 'fluid steel barreled double, liked that load with .69 cal balls and printed them together. The 192gr. charge of GOEX was too heavy, kicked too much, but also seemed to shoot 'centre'.
: The big bores really do provide a "Smashing blow" to the beasts of chase. buddy Keith dropped his single barrel .75's charge to 120gr. just to keep a ball inside a moose. That load didn't hit as hard as the heavier 200gr. charges, but still never failed to 'floor' a big bull.
: The 150gr. charge is plenty and should provide around 1,500fps or perhaps a bit better with T-7.
: My .69 shoots to the sights with both the 140gr. 2F charge and the 165gr. charge that I came to love for moose. The heavier charge merely makes the gun shoot a big flatter, barely raising the POI from the lighter 'heavy' charge.
: At a recent rendezvous, using 165gr. 2F GOEX, I never failed to hit the steel ram at 200 meters, nor a steel plate at 265yards, each time I shot them. While I wouldn't shoot a moose at that range, there was certainly enough "power" to get the job done well. At a more normal range of 100 yards, 'smashing' is the adjective to use, however any range within reason or your and the gun's ability is certainly just fine.