Do you mind posting the link to the check valve?
Also, I thought I would comment on the fuel line.
On my toy hauler the tank is in the back and gen in the front. At the factory they cut the rubber fuel line to short and stretched it across a sharp cross member to fit. I found out when I smelled gas inside the trailer while running the gen. There was at least 5 gal of gas on the ground underneath the trailer when I came outside.
Needless to say my rig has steel line from front to back with about 1 foot of rubber at each end now. Bottom line as rockhillmanor states it is worthwhile to crawl under and take a look from time to time.