I use 3/16" line with an 8 foot length served at 10 psi. The Perlick faucet is 1.5' above the top of the keg.
I also have a section of 1/2" copper, of which 3" is in the cold fridge to conduct the heat away from the warmer tower temps. Helps reduce the temperature change and reduces foaming on first pour (great tip from someone here)
Primary #1: Empty #2: Empty
Secondary #1: Berry Rhubarb Wine #2: Black Currant Wine #3: Ice Shanty Bock
Kegged: Border Crossing Vienna
Bottles: 2H IPA III, Carmel Apple Cider, Spruced Winter Warmer, Big 50 Barleywine, Framboise Lambic, Dark Belgian Strong, Russian Imperial Stout, Sparkling Elderflower Wine, Barolo Wine, On Deck: ??