I agree, not to much would be seen dropping it 10 grains. Limbsaver has a vew recoil pad out that takes up to 50% of the sting away. You may considder getting that. It took my 30/06 180 gr down to a respectable 22/250 feel. Pachmyer also makes one but it's not as effective, I put one on a 7stw and got it down maybe to a 7 mm mags feel. If it's applicable you may try the larger harris bipod model it will take a bit out and allow you and him both to shoot from a sitting position. One more option is the piece that straps over your shoulder that a lot of trap shooter use( might be called a recoil tamer).
Good Luck