Arnd, I installed minimal Raspian (with GUI) then used the 0.9331 beta image because it lets me shutdown PI from Actions screen.
Also, I found this thread on Metalmaslow that may answer some of the questions you had. I’ll have to look at Webconfig again but I think it had a Metalmaslow selection for sled size.
Haven’t gotten as far as you with setup operation yet. Hoping to get frame built this weekend.