you know, Jay, these things arent exactly that popular, few are the ones that go above 4 teams and even rarer are those that go beyond the 6 team parlay.
Books see them as free money and I can tell you they do not appreciate when you hit something large and depending on the book, they will try to get out of paying said parlay. I know many places have instituted a maximum of 2 dogs in a parlay (plus money) because the payouts really fly through the roof when you put in a few dogs in one.... Others will say there is a maximum of X/1 that they will pay on a parlay
I would say its not too many folks that actually sit and put together these parlays. The most I've ever seen hit in one parlay I think was 12. This was years ago, this lady insisted on talking to me when placing the parlays so she'd have to be transferred over. The second day or so she hit that, which in my eyes, kinda made others think maybe I helped her cheat somehow. What are the odds of hitting a 12 teamer, and on the second day of trying
She proceeded to lose back all if Im not mistaking.