Relative to bore capacity a 7/8 oz load in a 20 gauge is approximately proportionate to a 1 oz load in a 12 gauge. You won't find many super low-pressure loads in 12 gauge either for 1 oz loads. For true low-pressure loads in a 20 one needs to drop to no more than 3/4 oz of shot which is equivalent to the 12 loads of 1 1/16 oz.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra