Is this a workable format?

[The Armchair]

THE IDEA: A shootout style SnG. Buy in is $10 and play starts once you hit the magic number -- 10 or 8, depending on the turnout I'd expect and the space I have available. Assuming 10 players, the payout would be:
3rd: $10
2nd: Advances to Finals
1st: Advances +$10

Obviously, once you come in top 2, you're done until the finals. 3rd place gets their money back -- which basically means they get free entry into another prelim round.

After five prelims have run, you go to the finals. Payouts:
1st: 250
2nd: 100
3rd: 50
(perhaps I'd make it 200-125-75, that's not the issue)

The format for 8 players would be almost identical. Same buy-in and payout structure, leaving only $240 in the final round, or a $100-80-60 or 140-60-40 final round structure.

THE PROBLEMS:
How many players does this format need? Obviously, 18 is the absolute mathematical minimum, but that's not the practical minimum. I'm thinking 30 is the absolute bare-bones minimum.

How many can this format support? The flaw is simply that at some point, you risk having more people interested in playing a prelim than there are seats. I don't want a sitution where 12 players want to sit but, clearly, cannot.

Similarly, I don't want people sitting around for too long after they won their prelim spot early.

Finally, do you think people will potentially take 5 shots, buying in each time? (That may be a reason to flatten the payout in the later rounds.)

Thoughts?

[tubalkain]

Could always run multiple prelims at once, and instead of registering prelim winners directly into a final, schedule monthly/whatever finals so that if someone can't be fit into a final, there's always another one later.