...and the sooner the whole class has to buy new 7" wheels to remain competitive - in reality or perception.
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Whether sooner or later, that will happen. It is constant. However, the sooner the rule is changed, the sooner people will be able to take advantage of the cheaper and more abundant supply. That amount of people will be greater if the rule is changed sooner...it is time dependent, not constant.

How many people do you see on grid with 9# wheels - regardless of class and availability? It's less than 5% around here.
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You just made up that number! I'll look around and let you know. But, in general, i believe their are MANY in the 10-13lb range. However, 6" wheels are almost non-existent in that range *also*, not just the 8-10lb range (take a look back at my study in the "Oct fasttrack" thread). 10-13lb are comparably abundant in 7".