I never have liked the 'skinny spare' concept - so on my 1998/9 RF2 I found that a full-size wheel would go in the spare wheel carrier with no problem.
On my 'new' 2002 RF4 the carrier is mounted too high for this, so I made up 2 pieces of 3mm steel with 13 mm holes 50mm apart to drop the carrier - it hooks into the original brackets, which need unbolting to remove it. The holes need to be 13mm as the steel of the carrier is 12mm diameter.
The extension pieces were bolted to the original brackets with 12mm bolts and nylok nuts, hooked on to the carrier, then re-fixed to the chassis member.
I had to straighten out the side members of the carrier, but this was done with the spare in place, using a trolley jack to push it upwards gently.
I now have a full-size spare instead of the 'skinny' - I used the one salvaged from my RF2.