Tom, after looking at some of the data, I couldn't find similar loads using less shot in 20 ga.. I did find that there was lower pressure using a roll crimp over a regular 6 or 8 crimp in loads using the same componants.
Cheddite SR-7625 19.5 grs. 1 oz. CCI 209 SG-16 1142 fps 7680 psi 6 pt.
Cheddite SR-7625 19.5 grs. 7/8 oz. CCI 209 SG-16 + 3-.030 overshot cards. 1106 fps. 5265 psi rolled