You may know this already, but one reading of what you say here ("not a problem to have more weight in the back of the trailer") is very problematic. The trailer must never be loaded tail-heavy. If you meant, "more weight than I currently have in the back of the trailer," that may be no problem at all. But if you meant, "more weight in the back of the trailer than in the front," then that is a serious problem. Never do that! The trailer must always be nose-heavy.
The issue that people are raising is whether, with the tractor loaded forward, your trailer's tongue weight exceeds your towing system's capacity. IMO, the relevant specification is likely to be the allowable tongue weight of your hitch. I was recently surprised to learn that, even though I have a Ram 2500 diesel with a hitch that is rated for 12,000 lbs (1,200 lbs tongue weight), that rating is only good with a weight-distributing system installed, and without a WD system, my hitch is only rated for 3,500 lbs (350 lbs tongue weight). In that discussion, I learned that my spec is a little lower than typical, and most trucks nowadays come with a hitch rated for between 5,000 and 10,000 lbs (500-1000 lbs tongue weight) without a WD system.
I don't see a WD system on your trailer, so I would guess your hitch's rated tongue weight is at most 1,000 lbs, and possibly more like 500 lbs. I have a 16' tandem-axle trailer similar to yours, and it weighs about 1600 lbs. Say yours is 1800 because it's an 18-footer. My tractor is also similar in weight to yours, and, with a bush-hog, comes in somewhere around 4,000-4,500 lbs. If you also have loaded wheels, say that's another 600-800 lbs give or take. All told, you may be right around 7,000 lbs (which, on my trailer, with 3,500 lb axles, would be the limit, but you may have bigger axles on your trailer).
The optimal trailer loading places about 10-15% of the trailer's weight on the tongue. For your trailer, that works out to between 700 and 1,050 lbs. This means that, best-case, if you load the trailer just right, you may be right at the edge of some of your towing system's specifications. But if your hitch is only rated for 500 lbs tongue weight without a WD system (or, heaven forbid, 350 lbs like mine is), you are exceeding the rated capacity of your system even if you load the tractor perfectly.
In reality, a perfect loading is not going to be possible, because there are only so many ways the tractor will fit onto the trailer. My hunch is that if you backed the tractor on, you would reduce the tongue weight without making the trailer tail-heavy, which would be better. But if you have loaded rears, and if the bush-hog is a heavy-duty model, that might not be the case. What you can do is, measure your truck's ride height to the top of the rear wheel well with the trailer decoupled and resting on the jack. Then couple up the trailer and raise the jack and measure the ride height again. As long as the rear of the truck goes down when the trailer is loaded, you know your trailer isn't tail-heavy. At that point, whichever loading puts the least weight on the hitch is the one I would choose. The heavier loading might make for a better ride, but I would be worried about being so close to my hitch's capacity.
