If you have the Ford service bulletins, on page 250 there are pictures with dimensions of all the glass for 28 model A's. As far as the door window glass, it states 25 7/16" to 25 1/2" wide and 19" to 19 1/16" high. The edges are rounded and polished, with the bottom edge chamfered at a 45 degree angle with the angled edges 1/16" wide. The corners are rounded so as not to dig into the felt side channels. Hope this helps.
I should add, the picture Mitch posted looks like it is for a 30/31 door glass. The picture of the bottom chamfer and the rounded corners are the same for a 28.
I believe that Rem is correct. I rechecked and there are two pictures of the coupe/tudor door windows in the bulletins. The correct size is: 26 13/16" x 16 3/8". The corners are radiued at 1/4". I guess I should have checked more into the service bulletins. I thought they were always correct. Sorry for the misleading info.