Hot Fuel Lines
I would regulate the pressure as close to the carburetor as possible with a bypass regulator. That way a lot of gas get recirculated, only what's needed goes to to carb, the rest goes back to the tank. There is absolutely no way the fuel can get hot if you route the gas lines as shown in the below diagram. I had basically the same problem you are having and this solved the problem.
I would regulate the pressure as close to the carburetor as possible with a bypass regulator. That way a lot of gas get recirculated, only what's needed goes to to carb, the rest goes back to the tank. There is absolutely no way the fuel can get hot if you route the gas lines as shown in the below diagram. I had basically the same problem you are having and this solved the problem.