just found the lever head Park Tool Co. » 100-3C : Adjustable Linkage Clamp : Clamps

has me setting the bike down and readjusting the lever actuated clamp grip , and then trying again to get the grip and tube diameter in synch..

Where the EVT one can be cranked while you hold the bike up with the other hand ..

Lower cost Park has one of a similar concept Park Tool Co. » 100-3D : Professional Micro-Adjust Repair Stand Clamp : Clamps