I'm going the same route with my 11 yr. old this year. He also has a single shot 20 gauge, fixed modified choke, single shot. It patterned pretty well at 25 yrs. with the Federal Flight Control, 1 5/16 oz. #5 loads. I also want to try the same loads with #6 and the Federal Heavyweight 1 1/2 oz , #7. These are all MagShok loads and Federal has a rebate going to lower the price a little. Another load I want to try is the Federal high velocity 1 oz load in #7.5. This load would be less recoil and should be good for under 30 yds and carry about 350 pellets.

I added some weight in the plastic stock to bring the weight up to 6 lbs and a recoil pad, otherwise the recoil might be a problem for a young guy.

As mentioned above, have him pattern the gun load combination.