There is no perfect solution. Where are you driving that sway is an issue. One a flat road? Something is wrong. Having a solid base is a big help.
My F450 and huge sail was quite stable driving I70 when semi's were being blown off the road in April of 2022. My previous class C sprinter chassis 25 footer would have never been able to maintain 60 mph in those fierce winds. I was towing a 20 ft box trailer with about 3000 lbs in it. Again a solid base. The whole rig never felt like the wind was going to push me off the road.