I'll pass for the following reasons. Having looked at a 07 HR Navigator with a full wall slide I was surprised that the mechanism was not any different than my 17' LR slide with two large rails on the underside. The extra length to the rear was cantilevered off of the front...no additional supports/rail on the underside. Granted the extra length is mainly a walkway which brings up the change in access to the bedroom with the slide in...you have to go through the bathroom/toilet. Also the slide does not go out 33" like my LR slide.
From an engineering standpoint I would love to see how the roof is supported with that large a hole in the side. My educated guess is there must be a load bearing wall in the bath area with a beam cantilevered off it to support the roof in the middle of the hole.
My total area of slides (with 4 on my Navigator) is equal to or even greater than 2 plus a full wall slide that has 4+ feet at each end that does not slide or go out as far...this is not true of my 04 Dynasty with 4 slides as they are all several feet shorter.