I found with my small frame that my sides of my armor kept wanting to pop out, even with strapping and a very tight belt. I came up with this fix, working well for me so far so I thought I would share it will you all.   Fisrt found a few scraps of ABS, in my case these where 30mm x 40mm, but you can use any size you want. I then gave them a small bend so they would follow the inside of the sides. Roughed both surfaces with some coarse sandpaper and applied glue and clamps. I used two o