Mornin' Rose
I actually got that number from posts in the DIY forum. Seems I had read folks thinning from 10% upwards to 15% so I started at 10% and find it works well for me.
As for diluting the tastes of flavors well, I only vape unflavored so you'd get much better info from the DIY forum then from me (-:
It's good info to have

plan on doing some non-flavored. Do you get a little extra throat hit, with the vodka? Have read that it can be helpful in that department.
Racehorse: Hmmmm I've been looking for an excuse to buy one of those
Screamin Eagle: It seems to take an un-holy amount of flavoring to counter the water.
Been using iclear16 clearos on my MVP. They work great on it, and I like taking it out. It seems like the coils keep gunking up on the iclears. After 4-5 tanks they start tasting burnt and gross. The consistency of my e liquids looks right. Meh, maybe all the time with cartomizers has spoiled me. Get used to screwing it on, and using it for a few days to a week. Once it's done it's done. No dry burning, but having a carto go dry and not being in a position to refill...that sucks too lol.