I've been thinking about the fit of the back panel on and off all week - something wasn't right. Took another look this morning and again, there was definitely something amiss. In order to get the side panels (over the shocks) to line up, even roughly under force was very difficult.
So spent an hour with a fresh ground coffee and a laptop scouring blogs. A number of the recent and well illustrated blogs are for the GT chassis which has a different arrangement of panels at the back. But then I found it..... and it was (as usual with these things) as obvious as the worry lines on my forehead. The two stays linking the roll-bar to the back-panel were neither level nor the correct hight above the rear chassis. As I don't know what the correct height is, I adjusted them (brute force) bending them upwards slightly each time, keeping them level until the back panel fitted properly. Much better now. So much so I have started to drill the rivet holes for the final fixing.
I did get distracted at one point when I noted the proximity of the fuel tank to the mounting points for the rear warning lights. Would there be sufficient room for a rivnut? So before I permanently riveted and bonded anything I widened the mounting holes to 9mm and popped some rivnuts in. Then I needed to cut down the rear cases on the lamps for IVA before I could check that they all fitted together without snagging on the tank. I took 8mm of the back of the lamps with a fine toothed hack saw and used some IVA trim to tidy up. They now fit at 90 degrees to the road.
My work and home life have limited progress this week. Maybe I will book a week off soon and make some progress.