see what they've got in terms of spacers
polyurethane may not need the rubber to avoid scratching, so if you can get a 30mm long spacer instead of the 20mm like mine, it may make it simpler
or double up on the 20mm

the 20s i got have a 10mm bore, which is perfect for the bolts
i put loctite on the new 8.8 bolts as per PC's advice
tinus' suggestion to me was 8mm between the door and the carrier, and 8mm on the studs
in my case that wasn't going to be enough, so i just modded the carrier mount as shown
as it sits i cant fit my fingers through the gap between the tyre and the door, between 3 o'clock and 5, and 7 and 9