Paying out to 6 places is kind of rare, and using round percentages will probably give you weird payout amounts. Just an idea, but to get nice, round payouts something like this would work:
3/8 for 1st
1/4 for 2nd
1/8 for 3,4th
1/16 for 5,6th (get their entry fee back)
For example if the entry is $50, prize fund is $50 x16 = $800.
So that works out to:
1st $300
2nd $200
3,4th $100 each
5,6th $50 each