This issue seems to be gaininga lot of momentum. Remember that only a few of us will ever need this modification... since it's not easy to find dry camping sites in state & national park campgrounds that welcome 39ft+ RV's withopposing slides.
Also, this sounds like a less-than-straightforward retrofit - taking down the floorpans, modifying the 3" lines, stacked tanks, adding manual valves, sliding under the coach to actuate, warranty issues... ugh.
Once you fix this, it's timeto start thinking about a solar array. By the time your greys are pegged, your batteries will be depleted too. Lots of state/fed campgrounds have generator restrictions.
To the few who need this... you need it -butfor the rest of us, campgrounds with hookups are looking better & better!