Ok I will try the second method. It might seem an obvious approach to some, but the resolution of the tutorial doesn't allow you to see any boxes on the screen because the lines are too thin. That, and I'm new! Thx for your help both!

I was just thinking though, deleting faces would only work in a situation where an edge is drawn exactly along the length of the dog on the YZ axis. But, as the polys were converted from Nurbs originally, this won't always be the case, or will it? I guess I'll fiddle with cut faces in that case...