Ok,
Now I am finally on the same page as you guys.
I have always been focusing on the kitchen drawers.
Each of our kids (3 of them) have one of the "wardrobe" drawers in the rear of the caravan for their clothes which currently weigh bugger all.
We have the same "C channel" type fixing for the wardrobe drawers. There is only 1 screw in the front of the runner and at the back the runner is just kept in the "C channel". Looks like I will have to do something like you did Custy181 with some wood in between the wall and runners to provide more support for the runners.
I took out the 1 screw and replaced it with an 8 gauge 16mm screw and put some glue on it too.
I also took out all of the screws from the runners in the kitchen drawers and glued them back in and replaced some of them with 8 gauge 16mm screws and relocated some of the smaller ones to other parts of the runners where cables may be near. Crusty181 you are right, inside the drawer there is 9mm wood which the runners/drawers are built on/into.
Was good to check out the drawers and fix up the screws a bit because I discovered one of the drawers under the dinette table was loose due to the bracket (picture 6) that screws the wood to the floor was undone. I purchased some more L shape brackets to make it even stronger so it doesn't happen again (some of the brackets under the bed were also coming away from the floor)
https://www.bunnings.com.au/dreambaby-child-safety-mini-multipurpose-safety-latch-4-pack_p4210869
One of our friends with a Jayco Expanda believes the only drawer related issue I will have (on corrugations) is the drawers coming out due to the latches not holding so well but sounds like you guys have not had that problem?
If this is a potential problem, I thought of a few different ideas but possibly settled on putting the below child lock thingies on both ends of each drawer to the side in the hope they will not open.
https://www.bunnings.com.au/dreambaby-child-safety-mini-multipurpose-safety-latch-4-pack_p4210869