I suggest that with a typically flexible E9 chassis you won't notice a change in handling with the simple addition of a strut bar. The same as adding a bar to an already stiff chassis in any other car. It's the sum of many changes that will make a difference, i.e. stitch weld the chassis in structural areas, reinforce same, cross bracing, upgraded bushings, front strut bar, rear strut bar triangulated to diff / floor / chassis, Carl Nelson ( or similar ) suspension upgrade, tyre pressures, etc, etc. It would be interesting to compare someone's car that has all or more of these mods against a standard car. There will be an obvious difference In short - just a strut bar and nothing else will most likely be for appearance only. But so what?