says ~2.8 lbs a foot.....
Nope.
If that was true, I wouldn't be able to reach my faucet shanks from my kegs with a solid pour.
It takes 5 feet to get from Point A to Point B, and I run my regulator at 12 psi expecting 11 psi at the kegs through the two levels of check valves, and I actually run 6.5 feet including the flow meter section near the keg.
fwiw, I'll point out that 99% of the purported "line length calculators" claim 3/16" ID line runs at 2 to 3 psi equivalent resistance per foot (which is where the "5 feet" found on virtually every oem kegerator came from). My belief is this was the result of someone paying no attention to specified equivalent resistance vs pressure/flow rate, where resistance increases with rate of flow.
4mm ID is considerably tighter than 3/16", so it hardly seems likely that it would sport a similar resistance...
Cheers!