I'm curious why you wouldn't install the bars? Are you just trying to save a couple minutes? Do you have a bad back and are trying to avoid some lifting?
You say you are all about safety and your signature says "always do what's right". In my mind there's no question about what's right and safest.
Definitely use the proper sized ball if you choose to not use the WDH bars.
2011 Rockwood Signature Ultra Lite 8293SS, 12K Equal-i-zer
2016 Ford F-250 XLT SuperCrew, 6.2L, 4x4, 6'9" bed, 3.73
2010 Rockwood Roo 23SS (2012 - 2014)
2009 Ford F-150 XLT SuperCrew, 5.4L, 4x4, 5'6" bed (2012 - 2016)