If you are looking at the helmet straight on from the front, your right hand side has 16 stripes and the left has 15. Your pic of the stencils are left and right respectivly if you are facing the helmet
You may have to go with a RT-MOD helmet, I think your size is a bit to large for screen size helmet. Contact Rob at RT-MOD, he's really cool and tell him your size.
Look at this before you start the helmet, it will pretty much answer your qestions. The curved scissors are good for trimming the armor pieces. The finishing strips is where you will need a sharp razor and a metal ruler.
http://forum.whitearmor.net/index.php?showtopic=14806
The lexan scissors are a really handy tool, you can trim almost the whole kit with them and they cost around 10 bucks. ATA sends 2 pairs of ears in case you make a mistake. Take your time and have fun.
when using the hobby iron, I found that you dont want to keep the iron in constant contact with the surface or it will melt really fast. I just use padding motion and go back and forth alittle at a time, it worked well for me.
ATA would be to small for you, especially if you dont want shims. Like Mathias says RT-Mod would be a good option. If you could get down to 180lbs, ATA would fit you.
Looking good! The first suit i had i cut the cod and it did help alitle when bending down. I used to brew at home but had an explosion in the dinning room, besides I drink it so fast.
I have them on the holster where it mounts to the canvas belt. I think the head size is 3/8, the depth will depend on how thick your holster and belt are. You need 2 for the canvas belt and 2 for the holster strips. I really like these because you can remove them if need be.