Sorry, Wayne, been off the 'puter, hit and miss..........
Sounds like you got i right. The "fill" is the uniflow vent. You can run it to a tube facing forward, or hook it to the muffler. Muffler pressure does tend to even out the run just a tiny bit more from my experiences. Seems I have pretty much gone to using muffler pressure on all the non piped planes. It will change the initial setting of the needle a little bit, but things seem to run more constant and at the end of the tank seems to be more even when it comes to shutting off in a LOT of cases. I was running a square metal tank (no wedge on the side) on my OS .20FP BBTU and when I didn't run muffler pressure, it was very erratic when the tank was almost empty. Hooking the line to the muffler nipple made it shut down with just a couple burps right at the end. It also made the tank run basically completely dry, which it may or may not do without the muffler pressure.
Bill