Love this mod! It has many uses, such as adding ballast to trucks. Personally, I use this in my heavily modded Roamer that can pull the wind turbine trailer because the rear wheels don't touch the ground.
This is a great mod, well done, easy to use and lots of fun!
I have a suggestion for a possible future update. It would be great if the Grand Marshall could have roof bars/roof rack so that a crate could be put on the roof. Right now the only way to do so is to spawn a crate, put it on the roof and couple nodes of the crate to the car.