No free lunch when it comes to suspension. If you set the rear end to handle better AND handle the load, when empty it will sit high and run stiff. That is why Volvo did the Nivomats for some wagons- it allowed a level ride regardless of load. Sure, there are better handling shocks, but you can't have our cake and eat it as well. Air shocks might be an option, or air assist springs.
38PSI might "seem" to handle well, but logic would seem to indicate that it probably would not handle as well as would 33-35 or so. At 38 they won't heat up as well and will offer a smaller contact patch.Adding a stabilizer bar (anti-roll bar) would probably be the best start. Keeping the car level on corners is critical for handling.
__ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"