I've got a 4h steel stock trailer that I camp in the front of. I don't need anything PRETTY but I do want to make the front half a heck of a lot more watertight than it is now. Here's my setup pretty much as it looks now (although now it's Lexan instead of sheet plastic):

Here you can see the bolt-on horse corral.

And here you can kind of see the typical stock trailer door that doesn't go all the way up to the roof, but instead leaves a huge gap. 

I've sealed the roof ribs with silicone putty and it holds the water out pretty well. The water seems to mostly come in 1) over the top of the door, and 2) by running down the outside of the Lexan and then down the inside of the wall because the Lexan is installed on the INSIDE.

In case you're wondering... and I know you are... the corral gets in the way of putting Lexan on the OUTSIDE surface. If I'd planned ahead I'd have put Lexan up first, since I don't care if it's removable.

So.

How can I best deal with the gap over the door? Do I have no choice but to replace this door with something else? If that's the case where do I find what I need to replace it with?

How can I put the Lexan on the OUTSIDE now that I've got the corral there? (Can I? Or is there some better product to use?)

I'm not a particularly handy person, and neither is my hubby, so please use simple terms and explanations. ;) Pictures are best!

Thanks!!!!!!!!!!!!!!!!

A temporary fix for the gap above the door might be to use heavy duty magnets and secure a shower curtain or tarp over the door on the outside.  That is one beauty of steel trailers- you can use magnets for many things.

Good luck.