The other thing to note, the OP said it was windy. Was it crosswind, headwind or tailwind? Head and tail should be fine but crosswind ... oh my :).
As others have stated the setup is obviously important but conditions also dictate alot of things. We were driving from Houston to San Antonio along I-10 and it was WINDY and raining. Bad crosswinds. There were times myself and other large vehicles didn't get above 25 because it was so bad. My knuckles were white when we finally cleared the storm.
I have a 10K Equilizer on a Crossroads Z-1 (about 5K lbs). Regardless of the setup you will have sway on crosswind - the hitch and sway bars just lessen it. I have several RV friends who all have the standard chain/sway systems and some have upgraded to the Equilizer after seeing how it works on mine. Well worth the investment.