I've had the same experience as you, John. Can't stretch an extrusion grip. However, you can have a lofted surface be associative to two identical polylines and move the polylines with the dynamic properties to mimic the affect. The only thing I don't like is that solprof doesn't work on surfaces once you explode the block. Moves, rotates, and arrays work on solids, but you're limited to all the actions happening in the x-y plane. To make things easier I usually build the 3d elements outside of the block editor and copy/paste them in. Just gotta be mindful of the ucs.