how to replace the rear screen.

[nitroman]

I've completed my window now and I can indeed confirm that it does leak like a sieve at the bottom. I definately need to seal it somehow. Any suggestions?

Clear silicone sealant?

This is the best stuff I've ever used. You let it saturate into any FABRIC, unlike other products which DON'T want you to suturate the fabric.
http://www.303products.com/tech/index.c ... N=99304616

This works well on tops which have seen their best day, similar to the problem you describe. It will not however, seal a large gap.

[Galsia]

I spent the next two and a half hours putting holes around the new window.

Do you mean the laying the old window on the new and making the same holes made by the thread?

No. I just made a new line of holes about 5mm away from the edge ofthe window.