Quote Originally Posted by TGreen View Post
but the board should be at least 4inches wide. Can't really do that on a table saw.. Can I ? (36" times 4", 0"-3/4" thick). Table saw blade only goes so high, about 3inches high.
You are making a mistake here. The shim doesn't have to be 4" wide. It can be as little as 3/4" wide - all you do is slip it under the threshold on the outside, to seal the gap. Then caulk around the shim to make it waterproof. The threshold will rest on the foam you had there before.