We just purchased an 2007 Mako 29RLFW and had to search for the 'access panel' At the PDI the dealer found it under the fridge, to the left of the electrical circuit box. However, it was a sealed panel and the only 'access' to the hot water tank and the bypass system was to remove the circuit box.
We contacted Gulf Stream and ordered a cabinet door and hardware, pulled out the circuit box to pop out and remove the panel, then installed the cabinet door. Now the back of the hot water tank and bypass system is easily accessible. In defense of Gulfstream, we had a 98 Wilderness that also had an 'access panel' that was unaccessible. We had to remove a drawer to get to the bypass. A popped out panel and velcro solved that.
Campin'Corgis