Or better yet, just get a margin account and you don't have to worry about it.
My recommendation is that if you're a cash-limited trader you probably shouldn't be trying to "trade" this thing. I'd do a 90% SVXY 10% UVXY portfolio and just let it do its thing.
I wasn't telling Eric to buy with unsettled funds. I told him I sold my UVXY @13.42 . Eric said he couldn't because of settlement issues. Last I checked UVXY was at 10.12 And yes I wouldn't recommend day trading on a cash account.