why does everyone assume that 1-ways don't work on carpet?
They do, and are probably the fastest way round the track. Yes, they are more tricky to drive than a diff, and Yes, they are different to drive. But in a back to back comparison (unless your using foams), I'd take take a 1-way over a spool/diff anyday.
The only time I've ever found the need for something else in the car on carpet is when the track is super tight, or running foams.
Regards
Ed