Quote from trefoil:
From my perspective the idea is that these futures related funds, like VXX or UNG, have that well-known issue of roll-forward cost. XIV and GASZ take the reverse position in the futures, and both have a positive price history as opposed to the negative ones in VXX and UNG.
So the OP is proposing shorting both, an interesting idea. I would have thought going long the reverse and shorting VXX or UNG as a hedge, but I confess I haven't given this much thought, so I don't know if that would work. He knows someone doing something like this and it's working for that person, so that means there may be something to shorting both of them.