I went ahead and checked the instruction manual for the MORryde RV Cargo Sliding Tray - 90" x 26" - 2 Way Slide # MR87FR and yes you are going to have to crawl into your cargo compartment to fully secure the tray to your toy hauler.
The good news is you don't have to move the entire tray assembly in and out of your trailer a bunch of times, just the mounting rails so it's much easier to manage. view full answer...