Ok so I just bought some 16 oz leather and now in looking for a good pattern for a breast piece and back piece for leather armor, I check AA, although I may have missed it on my phone, a walk-through page would be nice as well.

i know of a document that might asist you, but it might take me a few days to dig it up. i cant remeber its name. but as soon as i find it i'll let you know.

Most of the time, any pattern for metal armor will work in leather as well. So Sinric's 15th century breastplate pattern would prolly work just fine. You could do just the upper breast/back and the front/back plackart, or you could try to add the faulds as well.

Found it, didn't take as long as I thought it would.

Billy, I personally recommend you go to here:
http://www.arador.com/construction/basicarmouring.html
and download "Basic Armouring- A practical introduction to Armour Making" by Paul Blackwell.
Its full of pictures and conveniently hosted by the Arador Armour Library.
http://www.arador.com/main/index.html

its in my opinion the best source of information on where to start and how to go about doing things from head to toe. as well as it itself has a large handful of patterns. and explains measuring your body for making gamberson which may help you tailor your chest piece to you better.

as well it also shows how to make a coat of plates. which i would recommend if your planing on a leather breastplate. plus if you like, I can show you how to hand sew leather. which in my opinion is better for strapping.

I made my helm from a pattern that I found in this document as well, redrawing and scaling it to size a few times until i was sure the pattern was the right size.

and you can't go wrong with making a pattern full size and with some help test pressing it against your self. to make sure its close. it helps to make it slightly bigger than you think you need. cause its always easier to remove access than it is to add back to it.

Ok, I bought a big fold of leather from Tandy Leather Factory in Metairie, the guys over there are great and gave me a few tips. I cut a test piece the other day soaked it in water till the bubbles stopped coming up then put it in 180 degree water for about 1 min 10 sec results the next day shrunk about 3/4 an inch but just about as hard as steel. I took my bullet proof vest for work which is already fitted to me and a protractor set at 3/8 of an inch and traced the outline. Plan on boiling this weekend.


Edit
The leather I bought is 13-16 oz

That sounds like a good thickness for the leather.

Be careful with the hot-water and leather soaking. Just a little too hot or too long will make the leather turn brittle. I have used this method on my hardened leather gear, and it works good. I have had a couple plates crack, though. I had also painted the back of each plate with 2-part epoxy resin. (like fiberglass resin)

Another alternative is letting it soak awhile in plain ole water, then letting it dry out on a form. You then 'cure' it in a warm oven (lowest settings) until there is no moisture inside. You could coat it with beeswax while its warm, or dip it in acrylic floor wax.

I've done the oven method with and without wax. Without the wax it does get brittle sometimes. It does get as hard as a modern plastic though.