I used a similar method on my first set of armor. I put the bolts on first, though, and chalked the tips to mark the fabric while the vest was on my mannquin. I think I did one piece at a time to ensure the chalk didn't come off in the handling. It's been years, so my memory is a little fuzzy on that.
On the inside of the vest, I had a plastic sheet insert that basically acted as a big washer with holes for all the bolts. The plastic sections, cut to fit each section of armor, sandwiched the vest.
On the new setup I'm working on, I was hoping to try the craft push pins, with the metal pinch clip on the other side (not sure of the exact name for those). Wondering how well they will hold up the weight of fiberglass armor, but I have a bunch of them. They would elimate some of the work if all you have to do is push the pins through the fabric, and it would also allow for ease in upgrading or changing armor while keeping the vest intact. Don't know if this will work or not, but I'll be trying it soon.
