It makes sense about the older bench shirts. If you don't mind me asking which katana are you using? The S/S model (90 degree arms) or the A/S model (45 degreeish arms)? Also do you bench with a big arch or are you more of a flat bencher?
I'm currently using a hand me down fury with a open back and although its a little loose for me (i can slip into the arms unassisted by still need someone to tweak it for me) my last PR attempt (missed it...but came close to lockout) was 345 at BW 150 and that still took a ton of effort to get the weight to touch. I'm still having a hard time believing your getting the most out of your shirt if your able to touch a new katana with 275. Can you give me a run through of how your benching, for example at what point you start tucking your elbows and what not?
And don't take any of my comments as undermining what your doing, I'm just curious as everyone has their own way of lifting in a shirt and I've been taught one way. Here's an example of how the guys I lift with set their shirt up:
Shirt Jack for Strengthworks Gym