resizing the apex

So I started Modifying the Back of a size 48 APT Apex 2 ply bench shirt today. Im making the back bigger so I can fit in it and still keep it a closed back so its wabdl legal. I tried it on with the back slit half way down.. wow this is gonna be the most extreme shirt I have ever used to date. This thing is fitting on me and feels just as stiff as an OverKill Shirt I tried that was my size. Since I have a 53.5 inch chest and I am gonna use a 48 2ply you should get the idea. It will defiantly take a while for the shirt to be broken in and usable for full range. Just 1st impressions I think it will probably take 700+ lbs to touch in. I guess its time to get to work on them triceps hard core...