Originally Posted by 68NovaSS
^^^ What???? Not much here related to the OP's post.
You're right. Let's go this way.....
Here is a product available from Eckler that addresses the problem nicely. What I would do is to purchase the product and a length of hose that the product requires and make changes to my system, using the proper hose diameter to fit the rollover valve. Having the rollover valve in hand would also present the opportunity to re-engineer the product to fit other sizes of hose and could lay the groundwork for producing a product for sale to others in your country. That's the secret to success, find a need and fill it.
Be cautious of selling against a filed patent though. Do some research.
Chevy Gas Filler Neck Valve, One-way, 1956-1957