not sure if this is what you're looking for, but this is what i use in the back of my expedition. it's big enough for three bikes. i can shift the rear tires over a bit so i can fold up the 1/3 seat in back so i can have a third passenger.
you probably wouldn't be able do do this in anything smaller than an expedition. maybe a chevy trail blazer, i think they're pretty long. maybe a mini van.
it's just a 2x12 with 3 yakima fork clamps bolted to it. i used 16 gauge sheet metal and some j bolts with wing nuts to secure it to the cargo tie downs.
