With a three legged trestle you would only need to put adjustability on the two outer legs. Twould make levelling relatively easy.

How big are the sections of baseboard, the lighter the baseboard the lighter wood used for trestle. (to a point cant go too flimsy)

7 hours ago, stevel said:

With a three legged trestle you would only need to put adjustability on the two outer legs. Twould make levelling relatively easy.

 

True, but until I know for certain about how much space I'll have above the boxed layout in the car I'm reluctant to add any type of levelling device. As a backup thought, the use of different thicknesses of plastic shims might have to be the option.

2 hours ago, TomCrewe said:

How big are the sections of baseboard, the lighter the baseboard the lighter wood used for trestle. (to a point cant go too flimsy)

 

The baseboards are 4ft x 3ft but an odd shape. The plan is for the trestles to support two L or U shaped beams with a couple of legs at the back.