Interesting question. I tried it. I gain about an inch of pedal engagement (an inch farther from the floor.)
Your adjustment method is how I do cars that have slots for manual adjustment. I have a 1966 12 bolt differential. It has no slots. I adjust as close as I can and still get the drum on then use the self adjusters for the rest.
The brakes were noticeably much improved on my last drive today, but they are still mushy. I looked further into the mention from pdlightning above about pinning the combination valve. I think mine may have been tripped but reset itself over time. I do not have a pin, but I believe that I will be able to make something work. Tomorrow's task then another round of pressure bleeding.
1950 GMC 100 Panel Truck, 1958 270, 3-spd Saginaw with BW OD, 3.73 12 Bolt Differential from a 1966 C10, Front Disc Brakes Hill Holder Bought it in pieces 9-1976, driving since 6-1978 Follow in the DITY | 
