I've got a 43' triple slide New Vision by KZ and all it has is D-Rings in the floor. Bolts go all the way through floor with nuts and washers. No way to pull through. Use a Pingel removable stop to lock the front wheel. From the looks of your rails I don't think I would want to put my faith in them locking down anything substantial. Looks like whatever was supposed to lock into the rail could pull out if enough force was applied. At the very least I would make sure that hardware attaching rails to the floor went all the way through with washers and nuts on the back. I know I would be sick to stop and find my Ultra Classic had fallen over and bounced around in the back because something had pulled loose that wasn't suppoed to have. Also, call KZ, talk to Sherley Miller she can tell you all the factory options that came on your trailer with the VIN. I bought mine used and they emailed me everything on it, also sent me owners and maintenance manuals. Very good people, also love this trailer even though I bought it used it is very well made and has many years of life left in it. Here is her number and e-mail.
Sherley Miller
KZ-RV
Customer Service
866-472-5460
-- email address removed --