I removed the pump screws and put a thick rubber pad under it and then left the screws loose a little. Both the inlet and outlet hoses go into the floor at the pump so there is very little I can do there. I agree with the water hammer part because the pump is very loud in the bathroom which is several feet from the pump and with a wall in-between. I bought some insulating material like is used in cars and tried insulating the "box" where the pump is located but no help at all. I don't mind paying the $70 or so dollars if it helps quiet things down.
This is brand new trailer but everything in is pure "China Junk." Very unhappy with the "stuff" in it.