Is my use of binomial distribution correct?

[asdfasdf32]

I had to relearn everthing I learned in high school about binomial distribution to figure out the probelm below (and by learn, of course, I mean found an online binomial distribution calculator). So, I'd appreciate someone making sure I'm going about this the right way.

PROBLEM: For the last couple of weeks of the NFL season I'm going to run a 7-game progressive parlay for some friends. The payouts online sports books give are:
7 of 7 - 40:1
6 of 7 - 4:1
5 of 7 - 1:2

Well, since the progressive parlays I'll be running cost my friends $20, I really don't want to be messing with a bunch of $10 payouts. So, I'll just up the other payouts to even things out.

So, using a 52% success rate against the spread for Joe Public, I get:

7 right .0102807 of the time
6 right .0664292 of the time
5 right .1839579 of the time

So, the sports book payout structure offers $15.38 of value per $20 progressive parlay.

If I payout $850 for 7 right and $100 for 6 right, my payout structure will offer the same $15.38 of value per $20 progressive parlay.

Does everything look kosher?

Thanks.