yep yep. I find that using "LINEWORKSHRINKWRAP" to produce a surface boundary often causes surfaces to be corrupt and not be able to be pasted. The command sometimes creates a boundary that is "not planar" to world coordinates and C3D doesn't like that.
BOUNDARY method definately best way to fix "problem" boundaries. Use it all the time.
Yeah shrinkwrap never quite gets it right with the 3d objects. I find i have to flatten them before using shrinkwrap and then it works.