I tried a moist hide when I first got the animals (a shallow deli-cup with a hole in the lid and damp paper towel inside). The boas would make good use of them, however, I noticed that regurgitation would primarily occur in the moist hide. So that made me think that the moisture was causing it. After speaking with a man who works on the microbiology (intenstinal flora) of bottae and keeps and breeds large numbers of them, I was informed that humidity is a killer (contradictory to Hoyer's site) in these animals so I decided to focus on bi-weekly soaks instead of constant exposure.
I suppose there is no magic bullet and some animals are just less fit than others.
Thanks for your help.