I have bowled about 8-10 regionals in my lifetime so far. I have finished as low as second to last and I have finished as high as 3rd, and everywhere in between. I know you said you don't want to be berated, and I hope you won't take this as such, but I don't think you are ready to bowl a regional yet. I think you need to find a house that will put down a sports patten or PBA pattern for you to practice on. Spare shooting is much different on these patterns than a house shot. Even though you throw plastic at spares now, do you hook it at them, even a little? If so, that won't work on Sports patterns, you need to go dead straight at the spares, and that takes some practice. Also how you adjust on these patterns is different, sometimes the correct adjustment is opposite what you would make on a house shot. Even if you do move the same way, it won't be as big of move as you probably make on the house shot. All these things take time to learn. Maybe you an find a summer league that uses Sports patterns in your area next year if you can't find a center willing to put one out for you. Also your "typical" shot won't play on a tougher, flatter pattern. While you may get a few stares and a few hushed comments about being a "shimwrecker", this isn't a team tournament where everyone is trying to play them the same. Feel free to play the way you think you will score the best, I have seen guys crossing 3rd/4th arrow on fresh Cheetah before. But I will tell you, that those who make the second day, and the finals, all seem to play around where "they" tell you to play these patterns.
The other thing to remember, and it was mentioned above, is don't put too much stock into the Friday practice session. Lanes keep a memory, and the memory is usually of the house shot. So the Friday practice session has hook left over from the house shot memory. On Saturday, the lanes will play tighter as the lanes has been stripped and the PBA pattern put down 2 or 3 times (depending on what squad you bowl on Saturday), losing part of the house shot memory. If you are lucky enough to make it to Sunday, the lanes will play tighter yet. All this plays into where you play and how you adjust.
But, even if you don't do any of this, that doesn't mean you shouldn't enter a tournament. I mean look at the USBC Masters and how many people have come from nowhere to win that tournament. Any weekend, anyone can get matched up and win. Try to find a patten that plays to your strengths....if you like playing inside try Shark where the shot will typically be inside. If you like playing the gutter, try Cheetah, etc.. Be respectful of the other bowlers and make sure you are aware of the courtesy rules. Dress appropriately including your name on the back of your shirt and PBA patches (which can be purchased at the Regional site). And treat the money like you would if you were going to Vegas, set aside the amount you willing to lose (the $300 entry fee plus high game pots if you want, new ball if you want to get one for it, etc.) and don't go over that amount. If you do that, you can try to have some fun and learn from the experience.