Perhaps due to blowing in it, my current BA Insulated pad just isn't insulating. Seems to lose heat during the night. That's why I freaked out and bought the Exped which had an R-rating nearly double the BA. Has an integrated pump so no need to blow moist air into the pad. Worked so well that I'm trying to find more ways to utilize it.
Sounds like if the 25" BA slips in easily, then I should be able to use the 26" downmat. I'll email the Jacks to see what they say about it.