Check out the Seattle RC Racers / Hanger 30 thread in the northwest forum.
We use square PVC downspout with most joints being slip-on using wood blocks that fit inside the pipe. We have a few custom corners with different angles, but our latest layout uses lots of Losi track dots (I haven't personally seen it yet). They are small and low-profile, so hitting them will unsettle the car and spoil your line, but it won't launch you into the air or cause a huge crash. They're fast to throw down / take up for our temporary track. Most importantly, using the dots moves the apexes away from the pipes, so you get unsettled from dots long before you tap a hard apex when you're pushing hard and cutting things close.
-Mike