Didn't mean to upset anyone. I was just pointing out that these Big Tex trailers are build tough. Yes, the mill is about 9 miles from my house and no Interstates involved, although I do pass under one just prior to the entrance to the mill. I'm not doing this commercially or for a living. I have been clearing my mother's property as she wants all her mature Yellow Pines down.
As for the Allison slipping, it will do that with no trailer connected going up-hill at WOT as the Duramax is chipped. If I was doing this for a living or on a semi-regular basis, then yes, I would absolutely get a CDL and probably a truck rated to pull this load or at the very least switch to "truck" plates instead of running "passenger" plates.
I used to run a Better Built 7 ton GN (very similar to the OP's Big Tex). Used it for a year and traded it in on the Big Tex. It handled similar loads without breaking a sweat, but I didn't want to chance it breaking down. My main concern with the Better Built was the brakes. They would strain under a heavy load. The Big Tex has monster brakes by comparison. Btw, I'm running a MaxBrake controller which is tapped into the hydraulic brake system on the truck. Huge improvement to have your trailer brakes come on instantly with your truck breaks instead of after. I had the Prodigy before and there is no comparison.
A secondary concern with the 7 ton was making tight turns on a hard surface with a full load and bending an axle. This is not a concern with the 10k Dexter axles on my current trailer, although it is painful to watch the tires struggle and change camber angle with a full load around tight turns.
Also, with regards to GVWR, don't forget to also take into consideration how much weight is on the truck axle. This weight is not on the trailer axles, so you can carry more than the numbers may imply. With a GN, you can carry as much as 25-30% on the truck rear axle, thus increasing the trailer payload accordingly.
Some pics of the Better Built getting a workout and definitely putting 25% or better on the truck axle:
Prior to the Better Built, I had a Hudson 5 ton trailer. Here's a couple of pic I found from 12 years ago. Yep, same old Duramax has been with me since I purchased it new.
Moving to a GN made a huge difference in stability. "Back in the day" I pulled with a SRW truck and a bumper pull trailer and wow what a difference my current setup is compared to that.