Changing topic slightly, but I had this bottoming out problem with the Fly Vette Speedvision but just on a smaller scale. The model has underchassis exhaust details and these ground out and wear away on the joints of my Scalextric Classic track. I used my Modellers knife set and cut most of these of, albeit, itb looked a bit messy, it ran. I used sandpaper to take 2 mm off of the area around where the exhaust detail was to make it reasonably flush wth the edges of the chassis. The guide was also slightly too deep for my track sso that received a good sanding down too and now runs perfectly.
I apologise for this being off topic, but just some ideas that some of you might be able to use on your Mk1,k2, XR3I, XR3, XR2I, XR2......Scalextric models.
Now, lets revert back to the original topic!