I am going to sound pollyanna right now, but I have been to lots of big meets and nothing serious has ever gone wrong and certainly nobody has walked off with expensive gear. Making alliances with those of us in the "hi-end" room will be adequate for protection and there will never be a moment when nobody you trust is in that room paying attention. That said, I would only have expensive woody things like the HE90 or R10 out when I was there or when there was someone watching my table specifically. Box them up for periods you are wandering and nobody is looking over your table. No guarantees can be made about this meet in particular, but past experience has been very good in terms of respecting gear (for the most part), lack of any theft, etc.