Did i miss a variable?

So, two days ago when I poured from the kegerator the first glass was half foam. The second glass was fine.

On another note. Out if curiosity I turned the gas off to the keg. Came.back the next night and every glass poured fine, regardless of time it sat.

So here are the specifics and please let.me know if something seems wrong.
Beer is kegged for 2.5 vols at 38 degrees. Which is 11 psi
I have 8ft of 3/16 which according to the homebrew shop is about 1 psi/ft.
So. I'm assuming the tap is about 2 psi of resistance. The height from tap o center of keg is about 2ft so that's 1 psi of resistance.

So do I need 8ft of line to make up the remaining 8psi. Or do I have something wrong? Did I forget about anything? Having the psi of the gas balanced completely with the resistance of the system?

Given the two instances of.foaming/not foaming any ideas?

8ft should be solid - first glass will pour foam from the remainder in the line. That will always happen unless you are pouring frequently.

I generally turn keep my gas where I want it to be pressurized for the vol. If that is lower than what I need to pour at I turn it up a bit, but only if I have a bunch of people over. I generally always have a pale ale on one of my taps so I have that length set to match the kegging pressure so I never have to fiddle with it. The other side is a longer line for kegging higher vol. brews or soda. That one needs to be turned up from time to time to get the correct amount of head.

If you keep the gas off too long and continue to pour off of it, the beer in the keg will begin to go flat.

Is there any pressure from the regulator that doesn't need to be balanced? Byo had something about needing 5 psi for a tolerate. So the system would need to have a resistance equal to the applied co2 pressure minus 5 psi.

It really just depends on line length. If I remember when I did the math for my pale ale tap it comes out of the tower at something like 3 psi. That's with the line and elevation canceling out the psi on the keg.

The other side has had a ton of brews in it - I don't get too mathematical with that one (other than the vols. it is kegged at). It has a 20 foot line on it so I turn the pressure up when I am pouring and down when it sits. That has worked great for me so far and I am still able to run a keg of Cream Soda (which needs to be extremely carbonated).

So what your saying is that height, tap, and line resistance you still have about 3 psi from the keg pressure?

So for me.
8 ft at 1psi/ft = 8psi of line resistance
Tap resistance = 2 psi
2 ft of height at 0.5 psi/ft = 1 psi of height resistance.

Adding together that gives me 11 psi to balance the regulator set at 11 psi. Should I have something like 3-5 psi left meaning I should shorten my lines?

Yea that is basically what I'm saying, but I'm no expert. Id say if it is pouring fine now leave it. You can also coil the lines on top of the keg. If the lines aren't hanging to the ground the resistance will be maybe 1-2 psi less resistance