Ok, here is the game plan for fixing the belt.
I first layed out where the back box goes on each side of the belt. This would tell me where I needed to cut and how much room I had to spare behind the box.
I took some extra ABS from what's been trimmed off the armor and put it together to make a couple long pieces. I doubled them up to give them strength.
Then I took these pieces and heated them up with a blow dryer and formed them to the shape of belt.
Once I had my pieces formed I put them on the belt to see how much room I had. These two pics show the open area and then with the box over it.
Now I have the two pieces clamped into the spots I needed them to be. This gave me the perspective I needed on the belt. I can secure the back part and allow the front be adjusted when I fit it.
After I test fit I'll continue with the repairs on the belt.