The other car was a NC based D Prepared Miata on recently rebuilt/valved Ohlins. Locally, our lot is bumpier than a cheese grater which probably part of the problem.

Most courses at Nationals have sections that have bumps/ripples depending on the line through them. This year the left/west/whatever had a section with a bump that was avoidable if you took it just right.

I'm going to have to stiffen the car more than likely. Moving to 23.5" diameter tire puts it into the shock tower/rear tub far too often.

The only bump I actually noticed was the one in the right hander after the slalom on the east course. 100% superdrifto'ed the entire offset section after it on my first run when I wasnt expecting it.

I might have slipped a bit with a hammer when installing my shocks. I like to use a big hammer. Its not too noticable.

5mm spacer is required with 15X10 6ULs on my car otherwize there is serious issues with the front near the shock tower and the sidwall of the rear will just scrape the two botheads just above the top of the rear shock in the wheel well.

??? Did you mean to say "isn't bottoming"...

I couldnt get it to move significantly with the hammer. And yeah I had my spinwerks made to the same offset as the 15x106uls + 6mm spacer. Still an issue, but not like complete death like the 6uls without the spacer were.

Doh. Yes

OK maybe a bit of angle grinder. It's actually thick right there looks more like the tire rubbed it off than you went after it with an angle grinder.

Hahaha!

Whatever it takes.

Hopefully someone can help me fully understand the relationship between front roll couple and balance. I'm in the process of overhauling my car and moving points around for the 2014 NASA PT/TT season in my 97. I was running 700/400 xidas with the thick wall racing beat tubular up front and the 14mm mazdaspeed rear. Car weight was #2105. Was was pretty good on smooth tracks lick road Atlanta but a little tail happy under acceleration at Sebring(bumpy). (EP air dam with no rear wing and 205a6).
I am now switching to stock swaybars to have enough points for a wing ( custom apr gt-250 like crusher). The "BTM" swaybars for the 97 are 19mm front and 11mm rear. So obviously I'm going to need to play with spring rates to adjust the roll couple etc.
After spending some time on the FCM suspension calculator I determined that the previous setup had a 59.3% front roll couple with an overall roll stiffness of 3900 something.
By using 900/400 with the stock swaybars it puts me at 60.2 % FRC or so with an overall roll stiffness of 3700 something. What affect will this have on the handling characteristics? I already put the 900's on but I haven't driven it.
If I went with 850/400 with the stock bars it would give me a 59.4% FRC.

Keep in mind I am planning on adding some weight, most likely around 100-175lb depending on how the new engine shakes out. And as mentioned earlier, will have the rear wing.

Thanks for any advice!

900/400 is a good starting point for your setup. I'd suggest installing brand new OEM end links. Theyre not strong and old ones might be suspect. Adjustables not an option with you points config.