backing into tight spot

newbie question:
I am storing the rig (34 ft North Shore) at a storage center. Currently there are a couple of boat trailers which are too long for their space right across from my spot. Although I'm trying to have this problem removed, my question remains.

If you have to back into a slot and what is in front of the slot limits the swing of the truck, what's the best way to set up? e.g., should your start position be about half way between the front of your slot and the offending boat trailers? closer to the boats?

Although practice in a parking lot will help my ability to judge this, I'll still face a tight spot when I come back to the storage center.

(It was a lot easier when I could just pick up the tongue of the Skamper and swing it around!)

Thanks for the help!