I used velcro the sticky back kind so i could stick it on my underarmour and on my pep bad idea i should have hot glue it but it was my mistake.You can use straps like stretchy straps connect all youre peices together.For example connect shoulder to chest then fore arm to shoulder ect.
Have you got a harness or sorts under the armor, over your bodysuit/glove/bdu? it's always a plus to have a main harness from which you can attach/secure most of your armor parts to. If you have, go with a combination of straps, velcro and snaps.
I strapped the biceps to the chest and back pact after i attach them them together. I had a webbing belt i had straps go down tot he thigh pieces to keep the up. The shins i used Velcro and left them kind of sit on my boots.
The arms i Velcroed to pads i used underneath them to hold it all in place. the crotch piece Velcroed to the webbing belt , sam with the butt piece
The best way to attach the shoulders/biceps is how Adam did it. Just watch his video. I did that using elastic and it work great. way easier to put on and take off than if it was attached to the torso! the legs I'm planning on doing the same way as Adam does it in the video. the torso I have in two pieces and the reattached with nylon straps, but elastic would would to, it all just depends on how you add them (glue or small screws). the torso can now be pulled apart (like a book) but not a lot and then I added straps like football pads: under the arms down at the sides of the chest. forearms, your glove can help keep them on or add padding to help. cod piece: just like any old belt. I used plastic backpack connectors/buckles (like on a life jacket) and the other things (i don't know what they are called) to adjust the straps (make tight or loose).
I would post pics if I had any. I might in the future.