Sounds like the blower(s) aren't the problem then....
You might have to wait until Bryan gets back to see what he has to say bout this. I know he changed the way the blower is handled in that it will start out with a spiked speed and then slow down to the actual set speed in order to help the blower start to spin in the lower speed range, but I don't think that should be causing your problem, not sure if any other changes in how the blower is handled were made on V10....
Just curious, if you put the small blower (5CFM) on and set the MAX blower speed to 100% does it do the same thing? I assume your PID values haven't changed/reset with the update? I know you had it dialed in before with the ball valve etc, but if you are not getting enough air flow with the max speed set to 30% did you try opening the ball valve a bit?