I just did something similar, putting a bulky forearm thing on a female arm like this. As a tip, you don't have to glue anything, just drill a hole through the gauntlet thing so it can slip snugly onto the forearm. Modify the hand's peg if you have to, to let it pop into the wrist hole.

This way it stays removable, you just pop the hands off, slide off the gauntlet, and pop in a normal hand.

Of course, if you don't want them removable, glue works too obviously lol

Dude! Your art is amazing! It's always so out of the box and intuitive. Do you have a facebook or instagram where I can contact you lol?