Water vapour barrier cork flooring
Hi, I've been in the flooring industry for a long time and have completed training on laminate installation as well many other types of flooring. The biggest concern you have for any laminate or click type flooring is moisture vapour migration. To put it simply it is a plague to pretty much all floors except ceramics and carpet where the effects are less observable.
I really don't know a lot about the construction of the undercarriage of the Airstream and its capacity to retard the movement of air vapour, however relative to the cost of the vapour barrier and the little bit of hassle during installation, it is a worthwhile investment. We install a vapour barrier under every laminate or cork-laminate floor, even on concrete on the 10th floor of a high-rise, as you can never be sure of the integrity of the substrate you are going over!! From reviewing many installations where vapour barriers were not installed and looking at peeking joints of the laminate or the expansion and contraction of the joints in other natural wood products, it would be a shame to end up with uneven and unsightly floors. This is, afterall your travelling home, and after all the hard work no one wants a failure.
This may not be the answer you were looking for, and I could be completely wrong (ask my wife she'll be happy to expand), but when it comes to construction projects, I'm very conservative and have a tendancy to over design and I've done enough things twice to know that once right is better any day of the week!
Cheers and good luck!