By the silence from the SWSRG boys I'd say that they don't care if their cars hit the floor.
Fly, the first set are just temp and will be removed and replaced as the scenery goes in.
Embs, I'd do something like yours but with the way we race, they'd go over the top. Example is Craig tried to stop me going over the top on the bridge of his old track. He failed, badly. Plus with the trucks ,you need something substantial.
Triggy, is that 3mm MDF wedged and glued into a slot?