The R90/6 with Ural is a sweet rig. I'd do it. Looking at the triple clamps I'd guess it is sorted out.
And the reach to the ground is a non issue with a side car.
I have a R/90S, it's beautiful but the riding position gets tiring real quick for my old wrists.
My blue R80/7 is Goldilocks.
The local Beemer shop has one of those in his shop. He also has a R90S in there. Of course I think he has just about one of every Beemer model crammed in there.
Has this really nice R90 rig he keeps tempting me with.