i was using a walker no shine contured piece on the front and then taping st-30 from where the walker ended to the remaining sfs to the begining of the french lace on a TL-500. My hair length is about 6 inches and 65-70% density. I was out in the desert in 115 degree heat the st-30 bubbled like you were saying yours did, but the walker didn't. Now I wasn't swimming in the thing.. (but close to it..lol) but it didn't bubble up and expand like the st-30 did.. at least not on that occassion