For anyone who is curious or planning on changing their rear springs this is the stock isolator and the prothane 6-1709 for the new edge Cobra with IRS. Probably half an inch thinner overall than the originals.

 

Very interesting.... just changed all my springs recently, I'd been thinking about the rear isolators and how thick they were.... for $28 on Summit, I might give these a try, see if I can close the gap in the rear wheel wheel even further. Looks pretty dang close, I just wonder how well they'll sit around the mounting bump on the body

 

link for them
https://www.summitracing.com/parts/ptp-6-1709-bl

 

They fit the body with no problem. The picture is a bit misleading because the stock ones have a tapered hole in the center where the prothane ones are the same diameter through.

 

This is how it sits with cargo coils in the back and moog 5660(?) in the front.

 

Here they are with Ground Control weight jacks/ eibach springs at full low in the rear, and raised a lil in the front so I can clear ramps. Easy install, and they fit perfect