When I first started with heat strips, my controllers were less then desirable. They worked great but heated so fast that I would more than occasionally get small air bubbles under the glass. This happened occasionally anyway, but I could tell it was becoming more frequent.
I changed everything that could be the culprit and then finally went back to the oven as a last resort...they went away...all but the occasional. I have never gone back to a strip.
i would say that my controllers heated the strips too quickly. I know that this could be corrected especially with my new heat controller...I use this with the heat strips to cure the overlays and tip overlays now.
My oven is "about" 80"s long x 24" wide by about 30"s deep with 3"s of spray foam insulation throughout. I mounted two 220 baseboard heaters at the bottom and two computer fans. I then mounted a steel plate above them with 6"gaps covered by expanded metal at each end of the steel plate. The heaters heat up both the plate and the air and the fans circulate the air around the plate and box.
With the insulation, it only takes about 10 minutes for the box to come to temp and will only cycle about every 20 minutes or so.
If I cut it on at 5:pm it will generally still be above 90 deg in the morning inside an air conditioned shop.
Works for me and probably only have $300 bucks in it...spray foam guy is my bud and has 5 of my bows .
the second base board heater is overkill.
BigJIm