I've posted and reposted this link several times in answer to people with draft issues. The factory still makes them nearly identical to my 2011 unit with the dropped frame. If you remove the pass thru storage rear wall you can look right down into the underbelly which as stated by DutchmenSport is no where near air tight. Here's some photos though dated showing nearly the same situation 10 years later.
https://www.montanaowners.com/forums...ht=design+flaw