Hi Ereitz! The "trim-convert" works only with a four sided surface, as it needs two directions for the "U" and two for the "V". Else it doesn't work.

Come to think of it, I dont think you can rebuild a surface in any way once it is trimmed, but there is an easy solution to it (I guess).

If you use the "untrim" tool under nurbs from the main menu, you loose your trimming, but you still keep your projection curves. So you can simply do the untrimming, rebuilding and then finally do the trimming again.

I have learned so much more about nurbs the last month, and it is real fun to feel confident about nurbs modeling.

I found a picture of the interior of the engine today, so the engine will be finished tomorrow.

Did you know:
That you can make maya insert isoparm at the most "preferred" place by shift klicking TWO isoparms on a surface, and then go to the options box for the insert-isoparm-tool, selecting the other "in between" option.

I'm not 100% sure why this is good, but I guess you get a more predictable surface if you rebuild later on. (maybe you dont have to rebuild at all?!?)