As well as pondering over the Silver Jubilee A4 details, I have been very slowly (even slower than normal for me!) tinkering with the D&S Coronation set that @ArthurK kindly sold to me (I have the MARC Models Silver Jubilee kit, but not touching that yet).
I tried a couple of times to roll a roof to replace the formed plasticard in the kit with no luck. I had already offered MJT extrusions but they were no good. Then I discovered that the Comet profile is a perfect fit.
Initially I tried to make one end slide out with a false floor but I couldn't find a way of getting it to work without issues with glazing, so finding a rigid roof is a bonus as I can make that removable - with the fairings under the solebar a removable floor is a non-starter.
Annoyingly, one of the first things I did was to get the bogies built up. I foolishly didn't check and they should all be heavy duty variants. The sides in the kid are standard ones, apart from the 10ft ones. So I will be removing the incorrect ones at some point and replace them with MJT heavy duty ones.