Being a somewhat new bowler, I think I can give you a good answer. I joined a league and bowled for the first time in January 2008.
As a new bowler, I was very impressed by the high average bowlers in our mixed handicap league. They all seemed to throw the big hooking ball, which of course, I could not do. At the time, I didn't realize these guys weren't the top bowlers in the area, just the ones who wanted to be the "Big Fish in the little pond". I didn't know the good bowlers were in the Classic Scratch leagues. Nor did I know that Scratch leagues even existed, and forget about the Sport Patterns.
As I learned a bit of control with my Ebonite Tornado, I started reading more about bowling and paying attention to the advertising in the various bowling magazines. The ads all talk about how much hook the ball of the month has. Hook rating is always a huge selling point on the balls getting the most "Buzz" as everyone talks about the newest, most advertised, biggest hook monster available. So what did I do? I went on some web sites and found myself the biggest hook monster I could get. Bowlingball.com has their perfect scale, so I got the highest number at the time. A Bruinswick Fury which was a 217 or something. Since I had no hand and threw the ball with muscle, it gave me my first 200 game. This caused several other bowlers to do pretty much the same thing, go buy a big hooking ball.
Why don't we listen to the proshop guys? Simple, the "better bowlers" in the leagues we bowl in are always coaching. We learn pretty fast that they don't know squat about bowling, except that they have figured out a way to make their way to work for them. And every "coach" has a different solution. Faster feet, slower feet, bend your knee, don't dip your shoulder, throw harder, don't throw as hard etc, etc. At some point, you just stop listening to anyone who tries to tell you what you need to do. Even if it is the proshop guy who does have the knowledge to help you.
My suggestion would be to have the current hot ball on hand and then something on the lower end of the scale. Don't tell them, SHOW them that you can hook the lower end ball. As my first actual coach said when she saw that I had the Fury and ask how it worked for me, "It's not the Arrow, it's the Archer"
I currently use a Lane Masters Buzz Attack, with a very high polished finish and a Columbia 300 Freeze. I also carry a Lane Masters Hornet which gets used quite often. Why no heavy oiler? I rarely bowl in the conditions for that as I have learned. The only time I use my Virtual Energy is for the PBA leagues.
Just my perspective on this, but since I have been one of the bowlers who only wanted the biggest hooking ball I could buy, this might help you proshop owners understand where we are coming from. We are ignorant, not stupid. Well, some of us anyway. :-)
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Nine in the pit with the Tenpin left standing. dooooh!!