Depending on where you plan to travel while towing, you'll find that there are speed restrictions in different parts of the country.
California has a 55mph restriction on Semi trucks and anyone towing anything. It's hard to maintain, but I can see the wisdom in not going faster. I teeter on the edge of 60mph while towing here, and feel real comfortable. When I towed my little 10' pop-up, it was all about the tire size. They just don't do well at higher speeds.