I use the R7/SM7 all the time in Colorado. I've never been on the TD's, my alternate tire is the Toyo RA1. The time diff between the R7/SM7 & the RA-1 is 3 seconds a lap at High Plains Raceway, maybe a little better under the right conditions.https://www.youtube.com/watch?v=pXILxQW0BaQ
I buy the SM7 since historically it's 50.00 per tire cheaper. It's the same tire
by designated SM for spec miata. The best price I've found is from Bob Woodman Tire.
Plus they will heat cycle them which for me is a big bonus
I didn't consider your particular tire size, the SM's only come in 205/50/15's