>This is just a thought...can you use the *rebuild* script on your build curves so than you can generate a single surface rather than polysurfaces?
It usually works for me when I'm working on a model where I don't care if I don't have totally sharp edges. They still look pretty sharp but have
a nearly imperceptible roundness on the edges and corners due to rebuilding the curves from which they were generated..

I've used that trick. It is the sharp corners that seem to split a single network into more than one surface. At times I've used quite a lot of points in my curve to make it look sharp when it really isn't. I've also found it is possible to add a point and then drag it to where I want the sharp bit to be.