We've done a rail out of a road signs pole. The diameter is about 50mm. Only problem is that the coating of the pipe doesn't slide well, so you should scrape it off (I mean with a rasp or sandpaper. Sorry for my lack of appropriate terms, I'm a finnish dumb.)
Dude, go to my pictures and look at my rail. make a wooden frame out of 2x4's or 2x6's. i use PVC conduit, the stuff u put wire in. it is cheap, and flexible and won't break. i can make rainbow rails with it too. i will hoefully have nmy new rail pics up soon.
'I wanna monster truck, Fuck the bus' - Matt Sterbenz after checkin out the Freezing Point bus.