Plates are 4 1/2" by 2 5/8", made from blue "barrel plastic" and tan 1/8" Kydex, depending on location (If I get hit there a lot, I used the thicker barrel plastic). In the chest area, there are 5 plates, with the edges cut down almost by half, to fit the curve of the arm opening better (cut verticaly). There are 13 plates in two and a half rows below that. See layouts below.
Whereever the diaganol lines cross, there is a slit in the fabric to allow the cords to pass through. I button-holed all the slits on the top fabric (black duck), but on the backing (natural canvas), I punched holes with a sharp leather punch, and then put in eyelets. Not sure if either of these methods will keep the fabric from tearing, but this way I can experiment, without the armor looking different on the outside. If I make another suit, I'd like to use brass eyelets everywhere; they install a lot faster than doing button holes, even with a pretty good sewing machine. The front of my armor has something like 118 button holes. Ick.
I used a soap sliver to draw all the criss-cross lines on the fabric, then cut out my pattern (taken from my gambson pattern). I then put the button holes at each cross point. The ends of the plates are clipped, to allow a small space for the cords to pass through. This also helps keep the plates from spinning. I'm lacing the plates in three at a time, going across. The cord is anchored to the back fabric, then comes up through the back and front fabric at the corner of the first plate. It comes up