Turns out I have no complaints about this setup in longboarding and sanding every square inch of the two doors by hand. Every square inch of the entire truck gets sanded three times using three different grits, so I really appreciate when something doesn't move while pushing and pulling hand sanders across the parts. With the doors out of the way, the next setup that needs to be engineered will be for the fenders.
This SuperJig is awesome, but not for a guy doing a frame up restoration of ONE truck. Its mostly for people thinking they will do a few more. It took me a few days to engineer the door setup and it takes about 4 days per grit to sand both doors. It will be a real time saver on the next set of doors for sure.