I was going to tell you that that trailer weighed at least 7-800 lbs, but I was wrong. Ish. U-Haul pegs it at 850 lbs with a max load of 1,650 load within it.
Your aerodynamics on Leroy may actually IMPROVE with the trailer. Leroy's worse than a barn door, and the wake is probably horrendous. The trailer may smooth out that wake, which would lessen the mpg loss.
But hauling a ton with a trailer that is taller than the vehicle, you're going to lose no matter what – when I towed a U-Haul 5×10 cross-country with my Talon, I got 8-12mpg over the 2500 miles. Of course I was often going "a bit" over the PSL. I had it packed, but not with very heavy stuff. Barely felt it though, even up mountains, and I was only running about 350hp. Turbos rock for high altitude.
You might want to talk to the guys running the race to see if they'll upgrade the trailer specs to 5×10 for next year. That allows a dual axle U-Haul, which is more stable, and you are MUCH less screwed if the trailer gets a flat.
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