Henry -
I have the L&H 2-wheel cart, and have been using it with a semi-grand
pedal harp for almost 3 years. It's light and convenient, and very
maneuverable. The tread is still there (except for one small strip
that was shaved off by a sharp rock). However, it's not rock-solid. I
think the plate that goes under the harp is a little small, and we
tacked on an extra strap (from rock-climbing webbing) that goes around
the harp base for safety.
-Sheila S.