Toy Hauler recommendations?

Yes, the sealed (and heated) underbelly is needed for winter camping, plus I suppose it helps to keep critters out. I actually prefer only the tanks and pipes to be sealed. My 5th wheel has a sealed underbelly on the whole underside, and while it may help to keep the coach a little warmer, it also makes it harder to keep the temps up around the water lines, since so much more of the underbelly needs to be heated. The Lance only seals around the tanks (and water pipes), and I think the Amped does as well. We spent a winter around Lake Tahoe in the 5th wheel and learned a few things about cold weather RV living. 1) Water lines freeze first, so that will be your weak link in your system 2) Just add some rv antifreeze to your waste tanks to keep them from freezing over 3) It is a whole new ballgame under 10 degrees F, or if the temps through the day don't rise above freezing. Thankfully, daytime highs in Tahoe were usually above freezing, but there were a few stretches where we had below freezing temps all the time.