Thanks Talkren!
I decided to shift my attention from the armor to the gaunts (still got the backplate to do which will need to be resculpted, but in due time)
So I had a set of test pulls from the Kydex lying around and wanted to use those since they came out good. Since these are thicker (.090) I had to shape them a bit after cutting them down to fit my skinny forearms better. I then sanded them and finish trimmed them
I've tried velcro in the past and am not happy with it at all, not to mention that it wears out and it just doesn't hold. In fact, I don't think velcro would work very good for these gaunts at all because they are so stiff. Doing magnets is a bit more time consuming and more expensive but when you're done, that's it. No more fussing and the best part? ...you don't have to worry about them wearing out.
OK so for the first step after sizing and finish trimming I marked my spot where I wanted the magnets to connect. I figured in the corners since that is where the gaunts will want to pull apart the most and will need the most pressure applied.
So, mark your spot and cut out some holes for the magnets to fit through on the BOTTOM shells. In this case, square holes because I'll be using cube magnets. I'm not sure what the strength rating is on these but they're pretty strong. I would recommend around a 5 lb rating. Not too strong, but strong enough for these gaunts. If you have .060 gaunts you may not need magnets that strong because they'll flex easier than .090. Enough talk, take a look
Cut the hole a little larger to allow easy passage for the magnet (but not too big)
Next I matched up my shell halves and marked with a white color pencil on the inside of the upper clam
Next I attach my magnets inside the upper clams where I marked, with some Loctite Plastix Bonder
After that I added some plastic spacers to the inside of the lower clams in order to recess the second magnet in order to allow passage for the initial magnet to slide all the way up. That will allow your clam halves to clamp together more tightly. This method is what I like to refer to as my 'peg and slot' method. The second (lower clam) magnet holds the first (upper clam) magnet into the slot while at the same time the first magnet acts as a peg. Since the magnets are holding themselves together inside the hole, there is no way the pieces can slip or slide one way or another until you take them apart (and even then they still want to go back together). Once they're together that's it. They're easy to put on and take off too. Another great benefit is that you can still take the halves apart and work on them without having to tear anything apart.
This will work on just about anything. (I used this method on my RC for the elbows attaching to the forearms and it worked great as well.)...you just have to think about how to apply it and which side will be the slot and which the peg

Take a look below and it might make more sense when you see the pics
Recessed magnet on the lower clam
Upper clam with cube magnet gripping tightly - peg and slot baby!!
This worked out so well and the magnets were strong enough that I only needed 4 peg and slots per gaunt (a total of 16 magnets). I was gonna add another one in the middle on each side but there was no need. These bad boys hold together on their own no problem
After that I decided to just go ahead and get them primed and let them sit over night
These'll be ready to sand tomorrow then I'll shoot them with some metallic silver and a coat of matte finish to seal it in and then it'll be masking nightmare for the next few days after that.
All in all, this whole process only took me about 2 or 3 hours (I broke it up here and there so it's hard to say exactly how long it took to this point). Not bad for the first day's work and it was fun to work on.