I've thought about approaching our local MTB trail spot about getting a track going. The simple fact is a U4 track doesn't require the maintenance a "fancy" off road track does. I figure anyone with a slash, revo or bomber could play on it. And I could incorporate a few off shoots for hill climbs and jumps.
A few years ago I had a axial yeti and a vatterra twin hammers. Really the only two examples of factory U4 trucks I can think of. Both needed a large amount of parts to stay together (the yeti ATE axle housings) and required quite a bit of maintenance to stay in decent shape.
That being said, U4 is my favorite form of 1:1 racing.