[Miniata]

I'd suggest taking your advice from fellow BRZ/FRS owners, but even that will vary widely. Better yet, try to find some other BRZ/FRS owners in your area with suspension modifications and get rides in their cars to see what feels right to you. You could also go to a local autocross, there should be a number of twins there, and most owners will welcome ride-alongs. We usually have at least half a dozen at our autocrosses, with everything from bone stock to heavily modified suspension.

Personally I added a front bar only to my BRZ, and was very pleased with the improvements in feel and handling. Did the same to my Mustang and Miata. My Mini is getting a rear only bar, and I've done just rear bars to other FWD cars in the past.