Are you having a steering problem with your Siesta? I have an 08 Siesta 24SA and it does not need a stabilizer. It holds steady when passing or being passed by semi's or other big vehicles. It moves a little with heavy crosswinds but it has never given me a white knuckle movement.
Glad to hear your Siesta is still going strong after 7 years. We aren't having any issues other than in high winds. We are new to motor homes so we really don't have anything to compare ours to. My husband is the primary driver and he said it holds the road fine (except for the high wind) but it feels a little "tippy". Not sure if this is "normal" or not.
My Siesta has Sumo air springs on the rear suspension. I assume the previous owner had them installed and they may be helping the ride.
He also had stabilizer jacks installed on all four corners but we have never use them other than to level it a few degrees.