I dont have an Anovos tfa suit, so I hope you can permit me to post my 02 cents.......
Placing velcro is a good idea and more convenient to put on or remove. I would suggest dry mounting the velcro to check gaps or if the velcro will show.
My fiberglass tk ab plate has velcro and we used the 'industrial' strength kind which I presumed is thicker than the regular. We created a flange that would conform to the depth of the velcro which was about 3/8" so the exterior look is flushed. Wearing it at first is ok, but after prolonged use you get to feel that 3/8" depth digging into your sides.
With your tfa forearm, you might need to glue a new flange where the other side of the velcro would mount to - this would naturally make your forearms smaller inside. This is of course when you close your forearm it would sit flush to the side and no velcro will be seen. But if you have large arms, it might not work.
Mardon (MLC)