Many of the Cougar XLite and Half Ton models have the holding tank slide valves "up under" the side skirt, mounted on the frame rail. You're right, they are a "bear" to get to. Many of us have taken a number of different approaches to gain better access. My approach was to install a door in the lower side skirting that allows a "direct approach" to the valve handles.
That mod is detailed with pictures (as are some other mods) in this thread:
http://www.keystonerv.org/forums/sho...ght=dump+valve
Whatever route you choose to go, please post pictures of your work. They will give other members ideas on how to make their trailers more "user friendly" ....