TVIX, which basically measures VIX futures, moves tick for tick with the SPY (inverse of course) with about a 3 second delay.
I'm using this 3 seconds as my 'stop loss' ... made 19 trades since 1:40p. Many of them were me 'pulling the table cloth' off from a reversal. Works well, at least in this market.
What's your average price, 29.75? You haven't been in profit yet on this short because you are fighting the majority. It's a lesson I have yet to learn but I'm trying to resist the temptation to initiate positions against the strong side. I hope you do get in profit for your sake, and I seriously wanted to short 33.25 but I originally had a long at 17.75 that did not get filled, and I think I would be shorting to get revenge for not having participated in this move up.
I'd say if 28 is penetrated then the longs will have to worry. Until then they have a higher probability of success than the shorts.
EDIT : FWIW, I think your short in the 30s was a great short, if you're going to go short. But bigsnack's EXIT at the same price was even better. I've just been burned so many times fighting like a salmon swimming upstream.