I don't know much about the processes but there was a discussion a while back re fermenters (my own experience, and might well have been solved) stocked at liquorcraft (Melbourne stores) that had underweight plastic used in their moulds resulting in weaker threads around where the plastic taps went in- resulting in leaks and taps that keep turning without sealing. All I'd say without knowing what's what, is to me mindful of the weight, manufacturing process and consistency cos even the guys who get this stuff done all the time have had issues. Not being disparaging but I know you'll be making a sizeable investment, so do the homework I guess. Good luck.