I'm brewing a saison that is traditional in all ways except for the use of Amarillo hops. I bought a "brew belt" to help achieve the proper fermentation temperature. When I get home I read the warning and it says never to use the belt on a glass carboy. I only ferment in glass. I call the homebrew shop and the guy says not to worry. He says that all the people he knows use them on glass and to just use a pillow case as a buffer. Does anyone else have experience with these "brew belts?" Any advice would help.