Anything over -2 is pushing it for a street 3 link car. That's a lot of strain on an already known problem area on 8.8s: the pinion seal.
The transmission of noise to the cabin is a part of stiffening up the rear suspension bushes and having a control arm attached to the actual pumpkin itself. It's part of the reason I went with the rubber Roush piece, especially since I'm not lowering. Putting poly LCAs did induce some extra noise but, it's very mild and only in a narrow speed range.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto N/A tune. 100 shot nitrous on BBR tune. Best e/t 11.38 at 120.85
2012 Premium GT, Candy Red, Brembo package, 3.73, MT82, Comfort, Tech, et al. Procal tune, Roush UCA, UMI poly LCA, GT500s, Steeda red bracket, Hoosier 28x10x16 bias drags. Best e/t 11.91 at 115.23 RIP