> Probably the best result for the kind of highly controlled blend that you are describing would be trimming
> a gap and then doing a 2-rail sweep with some custom profiles to >shape the blend, with an option to
> force the sweep to be smooth to the edges it is sweeping along. MoI does not currently have this option,
> but it is another piece that I >want to add in eventually... Again it is part of a kind of advanced toolset
> so it just has not been a focus for the earlier part of MoI's toolset.

This is what I have done in my model except the swept surface doesn't have the ability to maintain a G1 or G2 tangency blend with its adjacent surface (limitation of MoI and last time I used Rhino it didn't have this feature either). Even if it did I'm not sure if my surface will still buckle and twist due to the cross section transitions I need the nurbs to make.

Not to worry though, I'll keep on eye on MoI's future development and like I said will still be using MoI for the detail components of my aircraft where booleans are far easier to do than polymodelling them.