I soldered my return line as well when I discovered that the .090-.100 hole that was there would drop my fuel pressure at idle by 2 psi. I went slightly smaller around .031 and that only dropped the pressure by .5 psi, so I still have the same function of sending any air/vapors and some fuel back to the tank. I plumbed in a small fuel pressure gauge at the fuel line Tee (running 2 AFBs) so I could see what was going on. I've since corrected my other fuel problems (Carter mech fuel pump leaking check valves, clamp on line not tight and sucking some air when engine warmed up, return orifice too big) but I left the gauge in place. I've since noticed that when I shut off the motor, my pressure will soon drop to zero as the return line dumps any pressure back to the tank. My AFBs have a vent valve on the top of the carb and once the fuel/ethanol evaporates a small amount the float will drop and the line from the carbs drains down empty to the vapor separator. This is not really a problem for my set up since I run a small Carter electric pump in the back by the tank with a check valve in parallel. I run the electric for about 20 seconds to prime and pressurize the fuel lines then shut it off, and the hemi fires up quickly every time, even with points...
This may not be the best for every situation but it works for me. I even took it out in 100+ degree temps last Summer to see how it would act - all happy.

Jim