Until you hit something or stop "rapidly"

Then you have a 40kg missile....
You alarmed me a bit , so I did a bit of research.
The shear strength of a single 3/16 inch pop rivet is 350lbs.source http://www.crawfordproducts.com/multigrip.htm

Realistically shear load would be shared over a minimum of 4 rivets, and a maximum of 8 if using suitable webbing attachments which have some give.
So the minimum shear strength should be 350x4=1400lbs or about 550Kg.
So the impact would have to be about 16 G for them to rip out assuming say a fridge weight of 35KG.

I think you would have bigger problems to worry about in an accident with 16G force than your fridge moving.
In fact I do not think you would have any worries.

I think 3/16 rivet mountings are safe.
Now I am not an engineer ,so please correct me If my quick calculations are incorrect.

My Engel is mounted on a slide attached by 10mm bolts to 2 pieces of 1/4 inch steel plate, attached to the floor by 8 X 3/16 Rivets. I have further protection given by a dog guard further reinforced by 200Kg nylon straps attached to the rear seat belt mounting points.
Regards Philip A