Chris, thanks for the video: π
I tried watching and I got up to the point where you were trimming with the extruded cubes, then bamm the PC totally powered off. Not sure why, but it been happening to me lately with large (long) videos. (anyone a clue why?)
I'll try watching again at work.
The method you used which I did watch is similar to what I have tried. I just wish there was an alternative way to automatically isolate and delete the overlaps with out re-triangulation.