HI Beave, Bernoulli's theory, only applies tothe enterance of the pipe, that's why we use a Bellmouth.A stronger pipe, sure would have been better.
Rcpete

http://www.google.com/search?q=bernoulli's+principle&hl=en&rlz=1 T4GFRD_en&prmd=imvns&tbm=isch&tbo=u&am p;source=univ&sa=X&ei=TjQsT6CZOoWPgwfe-oDQDw&ved=0CEoQsAQ&biw=1280&bih=796

Also, when I added a small piece of 3thou ss, as a heat barrier, it imploded, at full throttle.
Fix was to go to 4 thou, and better, would have been the addition of a bellmouth