The main question for me is to figure out the angle, height, length, size of platform, any auxiliary features, fasteners to attach multiple pieces together, etc.
Angle of approach of the lowest longest overhang vehicle is the key number, I guess. How low is the lip on the lowest/weirdest car, and how far from the tyre centre is that lip. The flat part at the top only needs to be 200mm long, and at each end of that, a stopper, or bump. At the cliff-like-end, a highish/strongish stopper that will prevent over-driving accidents. And at the back ramp end, a little bump to let you know you're crossing the threshold. Maybe a D of brass or alloy or something, screwed to the wood.
My total height will be either 2 or 3 layers of these beams, thick. That's around 200-300mm or so.
If I use a separate piece for the stopper at the end, I can heavily screw it into all of the layers which will double to hold them all together.
Let me find a picture of the materials...


Refs: https://twitter.com/FredCookeNZ/status/ ... 7362990080 and https://twitter.com/FredCookeNZ/status/ ... 7139015680
ie, it'll need to be two pieces wide, too. Maybe 3 at the bottom, two on top? And if it needs more height after that, well, I can add more below.
Fred.