As for using your cruise control, set it and try it. If your truck "hunts" for the lower gear often while driving nor normal routes, then you may need to lock it down to 5th. With tow/haul on, that normally just keep the tranny in a certain gear longer to aid in acceleration. For the Fords, it also provides the engine braking.
Ed and Sharon
2010 Wildcat 28RKBS
2011 Ford F-250 XLT, 6.7L PSD
Ride-Rite Airbags and Airlift wireless remote compressor...nice!
I thought I was wrong once, but I was wrong!