Finally fixed the aluminium to the frame this morning. Used up some old silicone sealant left over from various previous jobs and stainless steel screws from my favourite boat chandlers (Ebay).
I haven’t weighed the roof but judging by the difficulty I had lifting the old one off and putting the new one on I’d say they are about the same. The big difference is that the new one rolls back easily.
And crucially on solo trips I can open one window and slide the roof halfway back to get out and deal with locks. There are quite a few finishing touches needed; trimming the windows a bit more so they open and close easily under the roof, tidying up the corners of the window frames and adding sealant, fitting a latch to the roof and insulating the inside of it. And as soon as the weather gets warmer getting the pressure washer out and hosing down the cabin and decks! One day I might paint the roof but at the moment the natural aluminium finish looks OK.