The v75 and VA suspension was a stop gap proposition to be sure. As you alluded too, I think
the Montesa engineers were "blind sided" as compared to Husky, Maico, KTM etc. It was very
hard to setup the bikes with the laydown suspension, as when let off the power, the rear tended
to pogo and the spring rate was critical for decent behavior. The lack of a decent tensioner or
guide and just plain terrible stock shocks didn't help matters. We also had some problems
with the tubing that the top mounts were attached to, bending. It was not a fun couple of seasons!
All was forgiven in 77' with the intro of the VB. Now days, V75's and VA's make good donor bikes
to make VR's. The VA 250 did make the most power of the VR, V75 motors, as the porting was revised
and they removed the exhaust bridge, and made the exhaust a big oval.