Fuel Return Line

The fuel return in my Sonex with 912ULS just goes back to the fuel intake line about a foot from where the fuel line leaves the main fuel header tank. Plenty of cool fuel mixing in with this returned fuel. 

Although it has only 46 hours on this system, I am happy to report it has worked fine even in hot conditions, and I haven't had any vapor symptoms to date.

I also doubt the logic behind fuel vaporization as any vapor is free to leave via the top of the float bowls in the carbs and as long as you have good pressure, vapor isn't really possible inside the pressurized fuel lines.

If the fuel gets heat soaked upon shutdown, just turn on the boost pump until full pressure is maintained and that too will vent any vapor out the carb float bowls and starting is back to normal.

My automotive Tech teacher taught us years ago that vaporization is just an old wives' tale and is not possible if your fuel pump has good pressure and noted the other reason as I mentioned above. Lots of experience over the years has proven his theory to be correct.