Depends upon which areas are his most sensitive. But if it's ony for two hours it had better be a decent stress position to which various elements like tickling or electro on a random timer or post orgasm vibro can be added. I think I remember you getting a sub in the stocks where he was standing ankles fixed, arms pulled behind and slightly up and into the wrist holes of the stocks so he was bent forward (sorry if this wasn't you). He could be standing on the evil mat, balls tied or weighted down, vibro strapped to where the head of his cock will just touch and the electro set to shock his balls at any movement. Blind folded and gagged to add to the sentence. If his balls are tied so as to make him bend his knees slightly it might make him try and change position more often - thus electro balls. I'm sure you can do better but it's a thought....