My son shot competitively for a few years, and I shot with him when he practiced. We both used O/U guns (Citoris) with my reloads. Neither was an issue after 100 rounds, and I can tend to be a bit recoil sensitive. Like Bob said above ..... you don't need a bunch of pellets to break clays. We shot 7/8 of #8 over a light load of AALite. It was a bit slow, but once you get the leads figured out it was money. Son could shoot 400-500 rounds a day with no complaints.
BUT ...... Are you using either a semi or pump gun? If so, the lighter loads may not cycle a semi reliably. In that case your only solution is indeed a reducer. Never used one so I can't comment on a certain brand. You might also try several different brands/loads in your gun to see if it will cycle the lighter stuff.