Hey Lee,
Since you have a travel trailer you may want to look at this
http://www.etrailer.com/Tools/Hopkins/HM09715.html I have had them on my last 2 campers and love it. It's adjustable so at the beginning of camping season every year I level the camper with a carpenters level to make sure it's right. The best part is it will tell you how much you need to shim the low side.