I'll toss in my 2 cents...
My
B8200 is about the same size and weight as your
B7800. I do not have a backhoe, but do have a rotary mower(longest implement) as well as a FEL.
I run a 16' 7000lb dual axle trailer. I have ladder ramps that stow on the side of the trailer(actually slide in from the side, in rails under the trailer).
Some notes from my couple years of use:
It handles everything I need. I can haul the tractor, PHD, scraper, and mower all together. When I do, I load the mower to the front, and let the FEL rest on it.
When my mower is onthe tractor, and I'm centered for weight balance, the tail wheel does hang over...
The trailer does everything I need for my CUT. The only time I have run in to issues, is hauling other peoples stuff... I have had to say no because someone else wanted to haul something heavy.
I have brakes on one axle. I am going to add brakes on the second axle. Although my CUT does not weigh that much, I would like the extra braking.
Mine weighs 1600lbs. That gives me a 5400lb capacity. My CUT is well below that(I added numbers and figured less than 3000lbs).
Some things to think about when you get a trailer:
Most trailers are really bare; you gotta add to them...
Make sure and get a spare. Most do not come with them. It will probably need a spare tire mount too... Not much is worse than having a flat with no spare...
Make sure you have a lug wrench to fit. It is probably different than your truck. It is worse to have a flat, and not be able to change it because you can not get thelug nuts off...
Add hooks and tie downs right away. Mine is set up with chain loops. They are "C" channel frame material welded to the trailer sides. Works, but I still want to add "D" rings in better places. Also, there are no hooks for tying ropes. I haul other stuff too. Rope hooks would be nice(I have a bunch to put on when I get time). A hook is a lot nicer to tie hitches on than a "d" ring or other loop.
Check in to jacks or bars to stablize the trailer when loading. When I have my stowable ladder ramps set on the back, there is still no support for the back of the trailer. When I load, all the weight of the tractor pushes donw on the back of the trailer, making the front want to rise, and make the back of the truck light.
Your prices are high. I Paid $1650 for mine new. Mine is a Carson brand.