Echo. Your tires are rated for 65 MPH and your Explorer has a very short wheelbase.
Go to
http://www.rvtowingtips.com/index.htm and read "how long a trailer?".
I hope some others chime in on the level of risk you're taking on at the speeds you've mentioned. I've got a 21 Ft. TV (yes, longer than my TM) with a 164.6" wheelbase, 5.7 L V8, my top speed is 70 mph.... and I got a blowout last Sunday. The offending tire has less than 7,000 miles and is less than 18 months old. Factory spec Marathon, air pressure checked before every trip and set to 50 PSI. I carry a portable compressor specifically to ensure proper tire pressure. Even with belt and suspenders, your pants can bite the dust.