Hey guys, I am watching Sky Greenawalt’s 36 Verts series and in Video 5 it seems to say that if you split a surface by isocurve with the shrink option that you should be able to match another surface to it even though MatchSrf doesn’t work with trimmed surfaces. I’m testing this and it doesn’t seem to work. Wondering if there’s a trick to it or if it’s a bug? 
Hi Cosmas - the limitation on MatchSrf is not on the target edge - that can be trimmed or untrimmed, but the edge being changed must be an untrimmed edge. By splitting on an isocurve and shrinking, that split edge can be untrimmed and not change its shape at all.
-Pascal
Hi Pascal, thank you for your quick answer. I understand the 1st sentence about the limitation on MatchSrf not being on the target edge but not sure what you mean by “By splitting on an isocurve and shrinking, that split edge can be untrimmed and not change its shape at all.” I wonder if you could please elaborate?
Hi Cosmas - an isocurvea are special curves that lie in the surface and can only floow the surface’s own structure - if you trim or split with one of those (ExtractIsocurve) then the trim will follow the surface structure as well and the surface can shrink right to that edge and not leave any underlying surface coutrol points dangling in space.
In simple cases RefitTrim can convert a surface so that the selected edge is not trimmed:
-Pascal