There's no way you're pressing 315 with a pause without gaining any size/weight.
I don't buy the 30-50lb gain from grip/arch technique either. That's a 20% gain at the high end.
I just started benching a few weeks ago so therefore my skill level of it is very low
Its actually a pretty technical lift
I just adjusted my grip last workout and I already come tell it added at least 10 pounds on my max
If I can arch enough to cut off 4-5 inches of bar path that allow will give me 30-40 pounds
3-4 inches off of a press is ALOT
I'm hardly even arching at the moment pretty damn flat I am and I take it to slight above pec level
Go to 5:30 here