Charlie
Have added safe-t-streer to several motorhome including my own it was more for the interest of safety and tire blowouts A stabilizer may not always help eliminate the way how the Motorhome reacts when being passed by a Semi, different chassis's suspensions have different handling issues. On the units I have installed the sate-t-steer i would say there was an improvement with steering control.
On a previous motorhome which was a workhorse chassis the biggest improvement with handling when being passed by semi's came from the addition of a track rod added to the rear suspension. this option may not be applicable to your chassis
Do you find that you have a lot of play in your steering wheel?, if so you may have some play in a front end componet, i believe the xc chassis's have a bellcrank which can be upgraded with an aftermarket product to help eliminate some play issues. Have tire pressures been set to tire recommend inflation charts
Handelling issues can stem from a variety of issues from tires, alignment, and worn parts and even inherent to some suspension designs