Here is my rig. I use it for my bird dogs as well. It also tilts and dumps for hauling other stuff. I secure it with U-bolts and straps.

I am in Kamloops BC. I sell the box for 799.00 Cdn + shipping. I am also looking for distributors in the US

I am building dog boxes in Canada. They are aluminum and hold up to 4 dogs...Let me know what you think...
Features:
Sliding doors so you can access your dogs without unloading equipment
Cargo rack so you don't lose the use of your pick up box
Cargo rack doubles as rig platform
Vents with covers ...