Honestly, dude, over last 25 years there were something like 50 occasions when VIX moved over 20%. Even if you would have happen to make money on all of them, that’s t-stat of 8. Accounting for the backfit (did you mention how many free variables you have?), that would be barely passable.The data for 2008 is not exists.. Look at 2011 how the strategy behaved when the VXX jump 300%.. One of the best year of the strategy..
If all the strategy is doing is going long vol when the curve inverted or went flat, you avoid a lot of them (no secret there). It’s still a short vol strategy and it is still subject to gap risk. I don’t see why anyone would pay a penny for this, all things considered.