Davy my thoughts are coming from more accidental ownership of a F700 16' flat bed hoist truck, 310B JD backhoe and tri-axle heavy equipment trailer. Take them with a grain of salt because unlike you I could not justify the purchase from a financial point of view so I spent less then $11K on the above set up.
Trailer: You expect to use it ever month or two months of the year for like a 30 mile trip with a load up to 7.5 tons. You would like a trailer that weights about 2.5 tons. If you wanted to really be safe you could say you wanted a truck that was rated to tow 15 ton (30,000 pounds) but one maxed out with your proposed 20,000 pound load hitched to your bumper or GN ball would be OK for the 30 mile pulls where you would not need to get over 45 MPH and still do the trip in one hour.
Not sure how much over 20,000 pounds your truck is rated to tow but I am sure you have that info.
As noted by another every ton you can shave off of trailer weight the less truck you will need. A tri-axle should tow just fine at 70+ MPH and while tire scuffing can occur when you have more than one axle at your planned 400-800 mile of use per year it is non issue. They are easier to spot and change a flat plus they have less drag if you are tracking the ground. While a tri-axle may be a few feet longer on average they may let you position your load better to manage tongue weight.
With the loads you are talking about that should not be an issue but when when I borrowed my BIL two axle backhoe trailer to haul the 265 MF without a loader but with a HEAVY 7' bush hog I had a negative tongue weight of 200 pounds. Not a fun trip hitting bumps and all that clucking going on but it was not issue truck wise thankfully for that 15 mile trip.
Being a man I have to say the dually trailer looks more manly and they are good for 25,000 pounds total weight.
Yes this is pro tri-axle post just because you have a pro dually post already.
You might keep your deposit until you "own" the 7.5 ton piece of equipment. If your 250 will only safely tow 9 ton or less you could look at a set up just for towing the few times a year with a nice older dump truck and a 12.5 ton factory build HD equipment trailer. Today that set up can be had for about $5K to $10K if you do not get fancy plus it gives you a materials handling truck. I went with a flat bed because I was reliving the past. :laughing:
The down side is the up keep of another vehicle. For my own personal use the insurance is $250 a year and taxes/tags is another $50 a year cost.
Let us know where you put your money.
