all the crews in San Antonio for this 'test driving' of the LIGHTNING didn't really have the time, or the place, to thoroughly test towing a trailer for the true 'range' for each type of trailer Ford provided. But, even then, it really is dependent so much on 'your' trailer, especially the HEIGHT and style of trailer, and maybe less about the weight of the item you are towing, though that, too, will add to the range difference, although to a lesser degree.
For instance, I own a small single-axle 16' camper, of the typical height and build as most. It is not very aerodynamic, of course, and the weight is in the 3,000lb range, or slightly less, especially if I'm not carrying a full water tank from the start.
I suspect each owner will see a varying degree of range difference dependent also on their geography. Flat roads at 55mph are going to be easier on the battery, while hills, mountains, and 80mph interstates will be much different.
If you are towing a 5,000lb flat utility trailer, with low height cargo, such as plywood or lumber, then you'll have a much better range outcome than the same trailer weight, but with a 10' high 'flat front' camper. The aero is actually more important than the weight, overall. A heavy trailer that is 'flat' is going to provide a lot more 'push' during downhills versus the camper, where the wind is certainly pushing AGAINST it, deferring a lot of momentum you might otherwise retain.
In short, as with all EVs that tow, range is cut by 50%, aero drag is the major factor. Regen is useful for recouping a few miles of range and relieving the friction brakes, but requires attention to getting max regen without using the trailer brakes (until required for control and stability.)
A great short-range tow vehicle with better software than we've (yet) seen on the EVlanche or R1T.
Note that "fast" charging is not a practical solution for towing beyond perhaps one stop to recharge to 70%. Charging is too slow to get to 70%, impossibly slow to get to 90%, and few charging locations accommodate a vehicle with a trailer.
I looking at my towing log for my 2012 F250 with a 6.7L Powerstroke.
Cumulative MPG is 15.2 over 9+ years
Non-Trailering MPG is 15.8
Trailering only trips MPG is 12.8
I'm getting 81% or losing 19% while pulling the trailer with a pretty consistent load.
The trailer is a 7' by 14' box with a V-nose, dual axle, I'd love to see the Lightning do as well, but cautiously planning a 50% cut until I have actual data.
My targeted charging location mid trip on race day is a very large Walmart lot that I can kitty-corner the truck and trailer into during the VERY early morning charging stop, I don't expect too much congestion.
note the 10/30/2012 event was a cross country road trip with many legs & fueling stops, repeating that with the Lightning would be challenging