I have bases fabricated from GW movement trays and VMC pumice/resin goop for my Sloppy Jalopy vehicles and Copplestone Castings vehicles, and at first had them pinned to them to reduce the chance of damaging them during transport. I found they looked too tall when placed next to my Copplestone & Artizan minis (which are mounted on GW round bases), so I removed them. Have not yet repaired the paint this stripped from the tyres, but as soon as I do (and repair some minor damages incurred during a move) I reshoot some photos of them and post comparison with/without bases.
Kenneth