Wow! Winter in Vermont in an Airstream. Exciting. I've installed a number of stoves over the years (never in an Airstream) and can only share my opinions and observations with you. These are mostly cautionary. I always use triple wall insulated stack pipe from somewhere above the stove thru the roof and up to the pipe cap. A few times I've used double-wall, but these stoves can get pretty hot, especially with a low ceiling penetration point. I love the boot product, and suggest using the silicone- again because of the heat concerns. It's good over 450 degrees F- but the outside of the flue pipe should NEVER get that hot. As far as your concerns about rib spacing, do a search here and you may find a number of pictures posted that show interiors under rehab - hopefully you'll get a good view of an area your considering going thru.
Follow the stove installation directions in regards to non-combustible materials (spacing and covering requirements/codes) to the letter. I'm sure you already have a smoke detector, but also it's smart to install a CO detector. A fire extinguisher is a must-have in any unit whether you have a fireplace or not.
You should be fine - plenty warm, especially if you're going to drain and prep the plumbing.
Best of luck and enjoy - post interior and exterior pictures as the winter progresses - is it snowing yet
so we can all celebrate your conquering the elements!