Well, after wondering about the way Thomas mounts their bodies to the frame, I initially only saw this as far as any form of mounts go:
but after closer inspection all along the outside of the frame and finding nothing, searching along the inside of the frame, I found 4 of these:
If this truly is the total points of connection (6), with the rear 4 being, in my opinion, rather wimpy, then maybe I should recant my initial statement of love for my Thomas bus. Granted, my bus is a shorty- 23' bumper to bumper, I still don't feel good about what I've found. The rear 4 "clips" aren't even very heavy gauge steel- a hair over an 1/8".
Hopefully I'm missing something here, because if not, I won't feel safe maxing out the load, and maxing it out's just my style.