Different sized barbs HELP!

I've had this recurring problem with my kegged beer getting foam on both ends of the line – foam at the shank and foam at the disconnect, with beer in the middle. This makes for a foamy beer unless the line has been just primed with another pour; and I mean JUST primed. This means I typically have to drink a nearly flat beer so that any guest can have a correct pour.

I recently realized that I've been using 1/4" ID line instead of the recommended 3/16", and that this may be the source of my foam troubles. So I bought some 3/16" line, soaked it in hot water to make it soft, and slid it onto the 1/4" barbed disconnect. However, I could not for the life of me get it onto the barbed end of my wall shank. I eventually realized that my wall shank has a 5/16" barb. (By the way, I was sold these two parts together at my local homebrew store Ferment Station in Knoxville, another reason why I now order online)

Basically, I've worked up a 1/4" to 5/16" double-male adapter so I can run 10' feet of new 3/16" ID line to 3 inches of 1/4" ID line at the wall shank. I'm serving at around 10 psi, and there's no more visible foam in my line, but the first pour is still foam.

Long story long, is the 5/8" shank causing my beer to foam?

OK, let me clarify. Is my beer foaming because its coming out of the keg from a 3/16” line and exiting a 1/4” spout? Could it be initially swirling around inside the larger area, causing the early pours to be foamy?