We purchased and installed the TST 507 last year in our 2022 - 1995. I installed the booster inside the curbside battery box. Simple installation - connect the wires and fasten to the wall. I have has no issues with this install.
I just read the manual and it states to install in the battery box on the front of the trailer. I would consider the enclosed battery boxes to be in front of the trailer, just a little higher.