Well, what can I say !! This is excellent, I had no idea. The speed gain is actually way more than 2x now that I can practically try it - more along the lines of 4x or even 5x in my case, this is excellent.

The opposite could be cool too (polyline to interpthrough by holding ctrl) - but then I suppose that interpthrough is not necessarily the "obvious" alternate, since someone might want regular control points instead. As a matter of fact both are equally useful, obviously.

In any case, thanks ! This is really, really fast.