Although this is a great forum for general kiting info, your board construction questions will be better answered at ;http://groups.yahoo.com/group/boardbuilding/
I put carbon-kevlar, then carbon right next to the foam in that order.. Then I add fiberglass layers.
My standard layup is : one full layer of 5.7oz. K-C , one full 5.7 oz. carbon or S-glass One more full 6oz, S-glass. On top of these three full length layers I install a large patch of 4oz. S-glass which covers the entire binding area and between the feet ... On top of this I install 1 or 2 small footstrap area patches depending on what type of board it is (light wind planer or high wind basher)...
Add the patches after the full layers are applied. You can feather sand the outside edges of the patches this way, making them blend in and disappear.
You don't need to use expensive materials like I do with the lay-up described above. Standard E-glass is good enough . Just make sure there's 5 to 6 layers directly under your heels and you won't have as many , or anybreakages again.... You might want to try plate bindings that have the aluminum or fiberglass plate covering the heel area. They are a bit heavier but they pretty much eliminate the heel dents that are the first stage of total deck failure............
I prefer to use S-glass for patches instead of carbon so the board's not too stiff.