I am not an expert on this but I am copying a post I just made from the bilstein thread. My setup was different than yours but what happened to me was I got coil bind in the front. I had too much travel at the ride height I wanted. I would say I fixed it but made it work with taller springs that had a smaller block height.

I made my own extended top hats. 1.5inch extension. I ended up switching back to normal nb top hats in the front.




Here is the setup I had.

95 miata with NB bilstein sports/NB top hats extended to 1.5 inch/Front 400lbs 7inch/Rear 300lbs 7inch/FCM 36mm bumpstops.

I used qa1 springs. I cut new circlip grooves 3inchs down on all the shocks. I put them on the car and set the ride height very low less than 12inch. It worked but was too low and I set the ride height to 12.5 Front/12.75 Rear. The front springs coil binded and pop the circlips off. I switched to ebiach 8inch 400lbs in the front and went back to stock NB top hats in the front.

 

The 1.5" drop is too much on the front. Measuring the avaliable spring travel before coil bind and looking at shock travel/ bump stop compression, I would have the bumpstop fully compressed before hitting coil bind with my 1" front spacer. This allows extreme compression to transfer load through bumpstop and shock mounting points instead of coil bind and overloading the circlips.

I am going to drop my front rates from 550 to 450, but luckily I gain 10 mm more travel with the new 7" springs so I will still compress the bumpstop fully before getting to coil bind.

 

Nice work. Those top hats look great.

 

I was thinking about getting an extra set of NB hats and making my extensions the same way. Looks nice and clean.