I have an 2010 F150 with 5.4 and don't have any issues pulling my TT with a yellow sticker dry weight of 5202. I am not accustomed to driving in mountains or even hills, so I do slow down on hills, but that is more a function of my experience with hills or mountains than capability of the truck.
I want to point out, please do not be confused by the names/claims like ultra light or light and actually look at the weights. My TT is a JayFlight which is not an ultra light but only weighs 5200 empty and is 28ft (24 ft box).
Also be sure as you look to check out the yellow stickers which is the weight coming out of the factory, not the published weight prior to production. The yellow sticker weight includes factory options, which can make a big difference (especially in available carrying capacity). I have seen some TT's with 500-600 lbs difference between published weight on website and actual yellow sticker weights.
