I had a choice of spray foam or rolled fiberglass.
I choose fiberglass with paper back .. wired to the ceiling.
The cost is lower with the fiberglass
BMWMOA 82741 ABC 8418
75 R90S , 77 R100 RS,88 R100GS ,94 R1100RS (Aragorn) 2k 1150GS DMC sidecar, R nine T