saddle pads should be used for padding, not for saddle fit. Ideally getting a good fitting saddle is the best route instead of taking a bad fitting saddle and trying to adjust it with pads.
Looks like you spent some time and got a saddle that fits, he shouldt need anything special now.
Lots of pads on the market with all kinds of doodads, bells and whistles. None of them will do anything better for a well fit saddle than a tucker southwest top coolback fleeece, or a reinsman canvas top fleece bottom pad. Both in the 70-80 dollar range. Good durable pads that do the job. I see alot of tucker cool backs on 50 and 100 mile endurance horses.