I am not interested in starting a heated discussion but wanted to share some information I found. First is a study from an University in the UK about trailer stability. http://pid.sagepub.com/content/223/4/471. Since I didn't want to pay to download the paper I was looking for articles summarizing the study and found this one http://www.sunbuster.net.au/wp-content/uploads/2013/PDFS/towballarticle.pdf. Thought it might be helpful for people having issues with trailer sway.