I managed to fit the rear screen and surround on my own this weekend.
Mark the screen centre on the glass and the fibreglass below, on a white sticky label with a vertical pen mark at the exact centre.
Fit the new screen rubber and cut to length. Use a putty knife to ease the rubber into position.
Fit the screen in the bottom of the rubber then I used a flat bladed screwdriver rotating it carefully to move the rubber outside the glass. Others use string in the channel and pull to open the rubber around the glass.
I had to get a new seal fitting tool as the original must be in a safe place. I put the nearest size end piece into the tool, clamped it with the allen key, and made the diamond shape as narrow as would fit around the sealing strip by compressing it in the tool, in a bench vice, using the sealing strip to check for size as I narrowed the tip opening.
Fit the sealing strip half a circumference away from the join in the screen surround so they are diametrically opposite.
To fit the seal with the tool, paint a 50/50 washing up liquid and water mix on the rubber with a paint brush, insert the diamond tip into the surround rubber, and feed the strip with your left hand, while pushing the tool with your stronger right hand. Start centre bottom, going to the left.
If the rubber does not quite seat properly, push it in with a flat screwdriver tip.
On the tight corners you have to use the tool at an awkward angle. Use it 90' to the rubber and slide the diamond tip side by side walking it around the corner, quarter off an inch at a time. pushing the sealer in with a wide flat screwdriver blade.
I have 3 more to do, so this is as much for my benefit when I do the next one, as for anyone else.
It looks perfect. Only a couple of dings in the paint with the screwdriver to polish out or touch up.
Now I have to work out whether to do the other three I have already done again, to make them look better.