Just out of curiosity (and not germane to the conversation at hand), why?
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This may shed some light. Back around 1993 or so when I first started racing a 2nd gen RX-7 I asked Bob Burns about using the 16" GTUs wheel (it was not listed as an exclusion at the time). He said something similar to the other statement about latest technology and that so many racers were already invested in 15" wheels.
Lo and behold, the following year that 16" wheel exclusion appeared in the spec line for the RX-7's.
Coincidence?