2012 Yukon XL Towing 30Ft

With either of those long wheelbase Yukons you will be fine. They're pretty close to a 20 foot long vehicle, no?
Get a good WDH with sway control and head out.

With the aforementioned "truck passing" you here is what I did when I was towing with my Suburban/30 foot travel trailer:

-as the rig approaches move over slightly to the shoulder, which increases the gap between the two of you.
-as the front of the rig reaches the space between your Yukon and the trailer is when you will notice your set-up getting a slight "pull" towards the rig. Slightly steer away from it until you can feel the "pull" subside.
-the rig will carry on it's merry way and you can center yourself back in your lane and start looking for the next upcoming rig.

This worked everytime for me.
Don't be fooled into thinking "you'll never feel anything with a good hitch". You will feel the "pull" regardless. You just want to alleviate it's affects on your set up.

Happy trails.

That trailer is so much longer than the SUV I would not do it. It's usually called the tail wagging the dog situation. When a truck passes or there is a wind gust that trailer will be shoving the vehicle all over the road. But I'm sure some people will tell you to go ahead.