I believe that if the heat rising is the issue, then the towel will probably not do the trick. That theory is based on the fact that the air in the room from top to bottom is warmer to cooler. The towel will insulate the bottom of the bottom enclosure, but the ambient air around the enclosure will still be cool. If that is the case, I am still sticking with my original thought that you need a larger heating surface on the bottom enclosure. This all assumes that your bottom heat tape is actually working properly.