Depending on where you travel, there's one more limit: The speed limit.
In many states, all vehicles with trailers are limited to 55mph, even if posted limit is higher. If you have to cover a lot of highway miles to get to your preferred places, this is a factor. Sure, you can plan to exceed that, but with my luck, I'd end up with a CHP behind me for 200 miles.
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[*]A well done expo trailer is an attention getter and security of it's contents and the trailer itself has to be considered.
[*]People even at a gas station want to talk to me about it.
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And positive or negative?
It's all custom... You'll spend a lot of time
Gas mileage, is the main detractor for me. Extra wind drag and weight, eats into and already low mileage average.