Slow going - my double storey extension build

[kingandy2nd]

Yeah, Alu doesn't flex as much so the process tends to be to fit it in at an angle with the beading near the glass, then pull it away from the glass to lock it in, and press the rubber seal in afterwards, which keeps it in place.
There also tends to be an order because they're butt jointed in the corners rather than mitred so you have to put eg the sides in before in before top etc

Thanks. Yeah, that’s how we did it in the end…also using the rubber mallet for a bit of persuasion where needed