Yeah, i didn't see anything underneath either. i do have chocks, they are travel chocks, i'm afraid to bolt anything to the floor since you can't see under!! the tie downs would be a nice add on, but not needed. i'll skip this DIY for now!!
What is nice about that Wheel Chock is that you don't have to mount it. It just helps the bike stay stabilized when upright to make it a little easier to get it tied down. I have used it to secure my bike in my snowmobile trailer.
When you type you can't see anything I assume it's covered with plasticor or coraplast or whatever that plastic stuff is called.
A boroscope which attaches to your phone has a 16ft bendable stiff cable and uses an app to record video and still pictures. It even has a light on the camera end.
12 to 20 bucks on amazon and ebay.
There is a picture and model info, and story about losing a hole saw in my black tank and the boroscope rescuing me.
Its in the link in my signature somewhere.
For 12 bucks you'll know where everything inside everything is.
When I added tiedowns to my nonThor toy hauler I ran them all the way through the floor to blocks on the underside of the vehicle. No floor tie in and the 12x12x2 blocks distributed the pressure/pull/torque.
The door side ones were tied to the frame and not the floor and passed up through slots, heavily silicone sealed.