KLXMASTER14/Robert.

I understand your post and I did find these pictures but do not use them myself.
I do use a constant tank pressure and a second pressure controller near the carb (like Cline) and that's oké for me.

When I see the pictures I would change the system as I show on the scheme of this post. So without tank pressure of the exhaust
The double vent line to the unpressurized tank probably gives a barometric pressure near the checkvalve outlet, one of the two lines has to be filled with air, the other is for retour of fuel. It does not matter which for what
The checkvalve does have a nearly constant pressure on the inlet side and that's also the fuel pressure on the carb inlet side, and that seems to be alright.
It has to be a checkvalve with little spring force to close the valve. The surface of the valve (A) and force of the spring (F) does make the constant fuel pressure (P).
The checkvalve mounted near the carburator!

It still is a study picture, so not prooved by me.

Cees


Edit : added some text details after second post (A) (F) (P).