On my RV, all I have to do to get access to the back of the HWH is remove a couple of drawers. My check valves would make too much noice so I took them out and just put in a couple of pex fittings. I also removed the factory winterizing valve. I installed a couple of new winterizing valves (1 cold, 1 hot) at the rear of the HWH. That way I don't need the check valves and am still able to winterize properly. I have had no problems with the hot water going into the cold and vise-versa.
p.s. I spoke with Winnebago reguarding the need for the check valves and they stated they are only needed for winterization assuming the factory winterization valve has not been altered.
2003 Sightseer 30B riding on a P-32