Thanks for replies.
I would make it clear that I don't want any surprises/accidents mid action.
My attention, and his, would have to be on the girl only.
I can imagine, it would only work if the guy enjoyed someone banging his woman. Not unusual nowadays and bit of a turn on to be truthful. On their profile both have escorted individually, so maybe there is less of a connection with each other.
Don't know why I titled "with a difference" maybe my cock's bigger than his, who knows.