In response to questions about the upper deck mod I had on my car at the Worlds, here are 2 pictures to explain.

The idea was to have the upper deck only attached to the front & rear bulkheads.

To hold the spur gear axle in place I used cut #53932 0.5mm roll centre spacers and the super low profile #51211 3x5mm flat screws. Then just raised the upper deck with 1.5mm spacers.

The cente hole on the roll center spacers together with the slotted opening at either end are perfectly spaced for the holes in the motor mount / right middle bulkhead so you only need to cut off a bit at one end of the roll centre spacer.