if you need complex 3D bezier-specified sheets i wrote some code which auto-generates them (and it's in python.) http://www.thingiverse.com/thing:13899
https://github.com/lkcl/pyopenscadspline does not exist
oh bollocks that's cos i deleted my github account because of their policy. ok grab this: http://lkcl.net/pyopenscadspline.tgz
Tried it this morning - not working either.