...it's possible STU peaked last year now that the dd Miatas moved to STL (a better fit IMO).
I agree STL is a better fit for the Miatas, but the STU thing is just a poor assumption on your part. STU's numbers are only growing here, and it has nothing to do with Miatas.
Here's a short breakdown of houston's regular STU cars:
1. Patrick Lindsey's retired World Challenge Mazda 6
2. BMW Z4
3. Solstice GXP
4. Another retired WC Mazda 6
5. Nissan 240SX (me)
6. BMW 328i
7. Audi A4
8. Retired WC VW hatch thingy (haven't seen him this year tho..)
9. 2nd Gen RX7- retired ITS car currently getting STU makeover.
10. retired WC Honda Prelude
11. Random SM double-dipper
12. That quintuple-entering Miata Jerry mentioned above
So out of 12 regular entries (we usually have 5-6 per race, pick any of the above and they could show up), only one, sometimes two are double-entering SMs.
Your region may be vastly different, but that's what I'm seeing in Houston.
There are also a couple others that are in the process of being built. one could be a Miata, could be RX7. either way, it will be a rotary, and it will be FAST.