Michael... I could not find the issue but here is the idea. Run a rope through the pipe, Curve the pipe and tie the outside ends together. The tighter you draw the rope the tighter curve you get. Then place it where you want and cover it up with dirt. The rope only helps maintain the curve until it's buried.
Composite decking is great idea...What type of base can I use if it's curved?
Not sure about drainage holes, I am afraid they may become import holes for water....?
Maybe pockets should be dug below the drainage holes and filled with loose gravel to help with the drainage?
thanks a bunch guys!