I don’t know the exact specs of that unit but 35 gallons seems like a lot. I would think 15-25 gallons would be more likely. Just plan on a lot of oil coming out.
IMO one inevitable failing to a dump trailer is going to be the battery. At some point it will not have enough juice to lift the hoist fully when loaded and it will happen at the most inconvenient time.
I ran heavy gauge welding cable under the truck back to the trailers hydro motor with a few...
The 4x4 off road crowd has a break lock that can be plumbed into your existing break system. It allows you to lock all four tires while not holding the break pedal down. I’m not sure if it works with ABS systems.
I wonder if adding some guy stays from the top of the grapple to the frame of the mini would firm things up on hard pulls once you build your up grades. Chain binder maybe or something similar, easy on easy off. Anyway it’s my brain overthinking it probably.