Hmm, OK, being able to flex the thicker Ultem sheet seems like a nice option for releasing parts, that's one big plus, I've often wished I could flex my kapton coated glass! As for Kapton pulling up from glass during a print, I have never had that problem. I have pulled up Kapton occasionally while trying to remove a part, but never during a print. Don't know if this has to do with the type/quality of Kapton. I've been laying it down on the glass after bathing the tape in water (no soap) then squeegee out the water and bake a while on the heat bed, after this the kapton adheres to the glass pretty firmly...