Ram owners. What gear while towing on highway?

I mostly run in 5th and 6th. At 70 it mostly stays in 6th even in hills. If I'm doing lots of up and down I'll lock it in 5th but it's not too frequent that I bother. For the most part the trans does a great job picking gears. My fifth wheel is comparatively light at a little over 10k.

My best non-towing trip of about 400 miles netted me over 23 mpg and that's in Idaho with lots of mountains, so I like the 3.42 just fine.