When I first came out with the Air Command, I designed it to use the KB 5gal seat tank. I purchased about 30 to 40 from him for the first Commanders I shipped, and every one of them would balloon up when filled, and you would sit down and gush fuel all down your back. Also he attached the fuel outlet by just threading a fitting into the plastic, which sometimes failed, and most of the times leaked. The sight gage hole was also just stuck into a hole with some glue.
Each time one went bad, Ken would mail me another to send to the customer, of course I had to pay the postage. After about 20 replacements, Ken refused to send more, and refused to fix the design. I was forced to build my own 5gal seat tank with the proper modifications to make it work right, and replaced all the Brock tanks I sold. Oh yea, I ended up eating the cost of all the KB tanks.
Later, Ken fixed some of the problems. I guess he got tired of replacing the ones he sold too.