I preach to never go more than 1/3 of cash publicly. I frequently use margin to trade VXX intraday and with swings. Last year my returns were practically criminal. I won't even repeat because unless you see the trades you would not believe. You must add to your VXX, it has diminishing returns of course.
For risk management you must be observant for that single day 20% pop which has preceeded all doublings of VXX. I doubt we will ever see one again like a unicorn with the controls in place but at 100% rise I would pare my bet back to 20% cash and start reshorting in 30 days from that moment.
You will outperform the S&P hands down! Even in a down market you would outperform hehe.
But this year the S&P has slightly outperformed being short VXX with 1/3 of your capital. I know you made made bank last year. There are guys on SPY board who apparently turned 100K into 5 million the past 18 months.