I've got a 2019 cascadia and I use a Steelie brand mount in the area right of the steering wheel and just above the 5th wheel release indicator.
In my 2016 KWT680 I have a blank panel where optional stuff would go. I cut plastic and used velcro to make a mounting surface.
Was watching a video and saw this driver mounts his in a location I haven't seen before and has custom mounting it appears.
New! Check out our help videos for a better understanding of our forum features
Go to Amazon, search for cupholder mount