Hi!
Carefully apply more glue and soften that holding the windshield on. Carefully tease the point of a Number 11 blade under the bottom. Work your way across gently. Now make a second pass. Be careful and do not break off the very fine point of the blade. This is important!
Now, very carefully, from the front, tease the blade under the windshield frame. Gently make a pass, then another, Do this til you feel a dis-connect. Do this again on the other side(We are doing the posts here)' Now for the top. This is the hard one. BEING PATIENT take the blade and again "Tease" it under the frame. Carefully drawing it across staying between the glass and the frame.
Here's the deal breaker for most. GENTLY, I can't emphasise this enough. Flex the frame, GENTLY! You should feel a further dis-connect. Now ease the glass away from the frame. Clean up all surfaces and wait twenty four hours for the extra glue to gass completely out. Now Clean up the residue(There may be some) of the old windshield. Do Not use another thick plastic windshield. take a piece of .015 Evergreen clear sheet. And cut a piece big enough to create a new windshield. Now Lay it on the OUTSIDE of your frame.
With a thin point grease pencil draw around the line at the inside edge of the Frame. This gives you the size of the clear area of the window. Now Draw another line 1/8" in the direction outward from the other line. This gives you the total area you need to cut. Now ,cut the top and sides until the lines for the frame and glass edge to just disappear. No more no less!
Your new "Glass" should be sitting pretty. Now take the excess off the bottom. There you have it a new windshield! With an edge to glue with all the way around. DO not use styrene glue! Use Testors'Window Maker or similar product. Clip in place, wipe any glue scooting out and let set for at least overnight. DON"T use to much glue. Only in the corners and high stress areas on the curve should do .This finishes the windshield. Now take a Sharp pointed metal object and gently, press in the mirror location. Gently now! This divot is where you will use a wee drop of (BONDIC, The glue pen with the U.V.Light in it!) Hit it with the light while bracing the mirror in the correct attitude you would see that mirror at.
Well, there you have it. I knew you could do it and Hey!, it looks great now doesn't it?