Use the classical tracker in stabilization mode and pre-compose the result to a target-sized comp.
The problem with tracking the speaker is that you're likely to get a fairly jittery move. It might be better to put a few keyframes here and there yourself to keep them in the shot instead of trying to track the whole hour.
You can apply tracking or stabilization information to null objects and then tie other things to them. For example, you could copy a null object with your tracking data into a 1080 comp. Tie another null object's position to that one with expressions subtracting the values. (Basically, value - pick whipped null object's position). Then parent your UHD composition to that second null.
Or, more simply, you could use the point tracker stabilization (also known as the legacy stabilization) on the footage in your UHD comp then nest that comp in a 1080 comp.
But, in either case, you'd want to take a copy of your tracking data and smooth it a bit first. Either using the smoother or adding a smooth expression to it.
I say forget the tracking entirely. I say animate the position property.
Make it look like a camera following the movement of the subject instead of a camera that unnaturally sticks to the subject like glue.
Tracking an hour long shot is kind of nuts and the results will be mostly useless. If your speaker is walking back and forth on the stage and he turns his body and he moves closer and farther away from the camera, and the most stable thing you can track is his waist, then you'll have problems every time a hand passes or he turns. You are also talking about some non standard frame sizes. Here's what I would do and it probably won't involve AE at all.
Import you hour long clip into Premiere Pro and make note of the frame rate. Create a new sequence that is standard HD and match the frame rate. When you drag your footage into the Premiere Pro Sequence it is going to ask you to match the settings for the clip. Don't do that. Now open up the clip effects panel viewer, enable handles in Premiere Pro Program Panel and then set a keyframe for position and scale. Move the clip into the right position and scale it to include what you want to include. Copy both the scale and position keyframes. Now scrub down the timeline and when you feel the need to change the position and/or scale of the shot paste then move down to the spot where you want the camera to stop moving and drag the shot to it's new position. Do this a few times, you don't have to work in real time, then select all of the keyframes in the timeline and use Easy Ease. Now you can scrub through your hour long shot and see how the moves work and make adjustments. That's all there is to it. You'll be done in about 1/10 the time it would take you to just get the tracking done in AE and you won't have to figure out how to fix all of the tracking errors. EZ PZ...