Can't help you on your windshield issue that you are having but as far as the floors go. Fiberglass is your friend!

We use MarGlas, which is kind of like bondo but has fiberglass in it, for smaller holes. Then for the bigger stuff we use regular fiberglass and rosin. Really easy to do. Just use some duct tape under the floor and then lay the fiberglass sheet on top of the floor. Mix the rosin and hardner and pour it on top of the sheet. Let it dry, paint, and you have a solid floor again. Yah it's not the "correct" way to do it, but for us, it is the way "we" can do it. We're not welders either.
OH, for really big hole areas, you can tape cardboard to the bottom of the car and then put the fiberglass on top. Your just trying to keep the fiberglass on top and not let it sink to far down toward the bottom.
Here is the MarGlas on my bus before I painted it.
Before MarGlas,

MarGlas on,


Good to go now!

I know I'm using your arch enemy for an example, but I havn't had to do this to any of my Pintos!

Oh, and as far as welding the windshield area, we are going to have to tackle a rusty windshield area in my Westy. We will be using MarGlas to do that job as well. Remember, we have no welding skills!
