I'm not sure an stl would help our process, right now I am working on a 4 cyl 16 valve drag bike head, the valve angles will be altered to fit larger valves, and intake and exhaust ports will be relocated for increased air flow. So, I'm not trying to make a surface map of the head, I need to pick off individual measurements of critical surfaces and design one step at a time. once you start trying to bring in a surface map, it start to feel more like your working with a bitmap than a vector file.
My workflow in a different cad program---
Start with the piston side of an intake port-
pick 3 points at the top of the valve guide and make a plane and a 3 point circle
pick 3 points at the bottom of the valve guide and make a plane and a 3 point circle
create an axis through the center of the 2 3point circles for the center of the guide
off this axis create a plane 90 degrees at the valve seat height
I think you get the idea, there are hundreds of different planes and thousands of points by the time your done modeling a head. Each of these points are entered into the cam software automatically by stepping on the foot switch on the Microscribe using the MUS software. There is no manual data input.
The MUS software can interface with just about any software, but it cannot interface with Fusion because there is no XYZ input dialog for points.
The XYZ dialog seems like a tiny issue, but it is one (along with a couple others) that are preventing me from using Fusion as my front line software.
TM