It shouldn't be hard at all to do it in 3d. You just need to create one half pipe section in say blender, use a converter (like my own) and just reuse the same model to the length of the "map" by simply using matrix translates. You could even do it with untextured quads and manualy create your vertices and polygons.Do you know if anything else is using LWRAM? If not I will go ahead and extend my jo_engine heap to use it as well.
Regarding using 3d for the pipe, I like the idea but I believe it will be above my ability to get it working before the end of the contest (~6 weeks).
It shouldn't be hard at all to do it in 3d. You just need to create one half pipe section in say blender, use a converter (like my own) and just reuse the same model to the length of the "map" by simply using matrix translates. You could even do it with untextured quads and manualy create your vertices and polygons.