This is important but hasn't been mentioned as far as I can tell.


"Lastly the benefit you state in Q-factor of baving bearings closer together is really a weakness in terms of BB stability and strength. Opposite bearing forces are higher due to greater moment aka Force X distance applied due to opposite crank arm"


I would wager if you rigidly mounted any type of BB shell in a fixture, fully assembled the different crank types and measured deflection at the pedal you would find PF-30 to have the most flex and a quality external bearing BB to have the least.