Thanks gents, that helps. Yeah, mainly looking at 1.070 OG or below for the 15 gallon batches. I've had these beers in buckets without blow offs so I wanted to be sure I wasn't getting too ambitious.
Using the spigot on top hooked to a tube for blow off should be pretty dang sturdy.....nothing to pop out....it HAS to follow the tube. At least that's my theory.