Here are a few suggestions. This is your tournament to run, and please don't take these personally, just giving you my thought process (I bowl a good amount of tournaments).
1) Why the large jump from $4000/1st to $1800/2nd? I like that you have kept 20th place over double your entry fee, but quite honestly you should spread that first place money out more. Unfortunately, everyone is so obsessed with "guaranteed" prize funds that many won't even look past the first place payout, then be upset when they get 2nd and are only getting $1800. The rule of thumb is 2nd should be AT LEAST half of 1st, and many would prefer closer to 2/3rds. The bowler who wins is a happy camper whether they win $2500, $3000, or $4000. But the lower places are going to think, "Wow, I bowled that well and was within ___ sticks of winning the tournament, but I only got some small percentage of what 1st place got". This goes into my next suggestion.
2) Pay at least 1:6, if not 1:5. Paying only 1:7.5 is in my (and other knowledgeable bowlers) opinion a cheap way to jack up the higher place payouts ($4000 for first in this situation). A majority of people are going to drive X amount of hours looking to cash, and if they get all the right breaks, win. But, only 1 person can win, so why not make 10 more people happy and pay top 30? Ideally, I would like to see a $2500 guaranteed 1st place payout, then $1400/2nd, etc. Use the extra money saved to at least give the last casher their entry fee back. The last casher will probably now end up +$200 on the weekend instead of +$80 (if they got in pots, brackets, etc), which makes a big difference (at least in our minds). There is a very large tournament run in Baltimore in August that guarantees $2500 for first and both squads fill up each year. The TD is able to pay 1:5 and give the last casher double their entry back. I think this is why tons of people attend, and many are bowling just to cash, because they know they will need a CAREER weekend to win. This is how you attract those bowlers who are on the fence; and if they see that huge 1st place payout and a low cash ratio, they will quickly decide not to attend.
3) More qualifying games! I say 8 games is a perfect number, which you are close with 6 games. But, I feel that with 6 games, one bad game can cost you whereas with 8 games, you can recover from a bad one. I am unsure how many squads you plan to run, but once again I will bring up the Baltimore tournament in for an example (as I believe this is one of the best run tournaments on the East Coast). The TD runs two squads, both on Saturday, at 9:00am and 4:30pm. 9 games of round robin match play is on Sunday for those who make cut. He even has a 6 game sweeper Friday night, which helps to make the trip worth it for people who will be traveling from afar. Many bowlers choose to bowl both squads, as there is tons of side action to go around.
4) The oil pattern needs to be more of a middle range pattern. I like that you make the lane conditions very demanding, but 48 feet flat really freaks people out (unfortunately). I would like to see something in the 38-41 foot range that can cater to many styles of play. Many people will hear 48 feet and say, "Well I can't rev the ball up enough to score on that!" which we know is completely untrue, as you can rev it up all you want and the ball will not think about moving. Basically, you might be scaring people away with that long of a pattern, and think a medium length 2:1 ratio pattern would cater to more bowlers.
Again, these are only suggestions, but if you do decide to take these into account, I (along with several other of my friends) may entertain the idea of driving down there. Hope this helps.
