It’s the last bit that’s the problem getting a loaded trolley onto the base I find and that can be because the trolley wheels are lower than the trailer base.
How about putting the trolley wheels onto ramps so that the trolley is the same height as the base then the pull will be forward, rather than UP and forward ?
It sounds right ???
I have always had the idea that if you use a winch to pull a loaded trolley your bend it across the aft end of the base.
I would say that the winch needs to pull on the trolley axle,rather than the front. ??