ISC racing tophats...warning...

[wannafbody]

I've had the ISC racing tophats/NA bilstein combo for a few years now. I'm using them in conjunction with 46mm bumpstops and 550/350 springs. I added a front shock packer due to wanting to avoid fender rubbing. In the rear I used the recommended 1.5 inch tophats. My ride height is 13/13.5. At these heights I never had an issue with control arms hitting the chassis or rear fender rubbing but the rear always felt a bit choppy. For kicks I ordered a set of 1 inch tophats and installed one side. I went for a quick ride down some backroads and felt as if the ride quality improved most likely from the 1/2 inch of additional droop. So IMO, save the 1.5 inch tophats for the slammed crowd, for reasonable ride heights the 1 inch top hats are plenty.

[Massiah]

I find NB tophats to be enough. I'm currently running MSM Billies with 550/375 6" springs, stock NB tophats and cut NB bump stops. 12.5"F/13"R and I've not touched the bumpstops once, so take that for what you will. Little off topic but related :)

[MX5RACER]

The original Koni race valve shocks, for the rear on the Miata, were coming shortened. It was discovered the with a shortened shock, extended top hats etc. you would actually run out of droop travel and cause strange behavior. They now come as standard length. Might be a little bit of what you were experiencing.