I started a post about the exact same thing a couple days ago. Got lot of good answers and points. I've already got the second way bar and got it ready to go. I am leaving next weekend for a road trip for a week. I've been pulling trailers for 20 years and I think I've got hang of it. I always put max pressure in all the tires. In the past I've had only one friction sway bar. It didn't sway going down the road but would only wiggle when a semi would pass.
Last trip I did tighten the sway bar up tighter and it did make a big difference, thats why I thought I'd try 2 sway bars.
I will let you know how it worked after the trip next week (9-22).
I am quite confident 2 friction sway bars is a good way to go. I bought the used sway bar on craigs list for $25.00. Bought the 2 balls for about $15 each. I welded the 2nd arm on my hitch myself.