Definitely agree with above posts, stick to published recipes. That said, when it comes to recoil (at least free recoil which is controlled by the round vs felt recoil which is controlled by lots of things like firearm weight, action type, buttstock pads, etc), its all a question of physics, ie Newtons third law and more specifically E=1/2mv2.
You can control velocity to some extent with powder type and charge weight, which you would think would have a greater effect given that its role in that equation is squared, however in practice, the different powders and charges dont in the end create a huge change in velocity. The mass of the ejecta, ie the shot weight, is the easiest most noticable way to reduce free recoil. Mess around with powders and their charges all you want, but as others have suggested, dropping to 3/4oz load from 7/8 will get you better results than anything else (at the cost of less pellets being thrown at the target, thus lower odds of a hit with suboptimal shot placement.) Once shot weight is reduced, you can then work on finding a powder type and charge that minimizes velocity fur full recoil reduction.
Have used these tenets for my cowboy action loads to great utility. Spent a lot of time replicating Winchester lite loads (which are a (7/8oz 12ga load) and which have a reputation for being a light load. Well after finally figuring all this out, switching to 3/4oz loads with the claybuster wads meant for that, I got my most dramatic recoil reduction by far.
