Velorex 562 18” wheel?

I have a 1982 Velorex 562 on a 1976 BMW R75/6. It has an 18” wheel. Everything I’ve read says it should have a 16” wheel. The original owner and rigger was Perry Bushong who was known for great handling sidecar rigs. But there were a couple owners after him so I don’t know who installed the wheel. The bike seems to have about an inch too much lean out so I think the 16” wheel is what it needs. Does anyone have any advice on this? And does anyone have a used 16” wheel for sale? It handles well but the wheel is really tight in the wheel well. Thanks in advance!

1. Define "tight" in the wheel well. Dies the tire polish the paint inside the fender when tou bottom out the sidecar wheel?
2. Does the rig track straight "hands off" at normal crusing speeds?
3. If the rig was assembled by Perry then I would expect that it does handle correctly and that he installed the 18 inch wheel to take advantage of the wider availability of suitable sidecar tires. Just a guess. I worked for him for over 10 years and saw and learned a lot from the experience.