Those calculators/charts are used for commercial draft systems, and the only thing most of them do is calculate the line length that will result in a flow rate of ~1gal/min. This works for most commercial systems because the beer is stored and served very cold. The warmer the beer is, the slower the pour needs to be to prevent foaming, and 1gal/min is too fast for most beers at 42°. Unfortunately those calculators and equations aren't valid for any flow rates other than 1 gal/min because they assume a fixed line resistance, but line resistance is actually a function of flow rate.
The only line calculator I've seen that accounts for different flow rates (and therefore variable line resistance figures) is below. It allows you to input your desired flow rate in terms of the time to fill a pint. For 2.2 vol at 42° I'd suggest something in the neighborhood of a 10-12 sec pint fill time, which for you means 7.5-10.2 feet of beer line. Also keep in mind that it's much easier to trim a foot off of a line that's too long than it is to replace a line that's too short. And as mentioned above, there's no disadvantage to longer lines other than a slightly slower pour.
https://docs.google.com/spreadsheet/ccc?key=0ApGb-vIKLq7FdGtzN3BrY2xZSldORzQ2bHVVX0hzaEE#gid=0
It only seems to defy the laws of physics because the equations used all assume that line resistance is a fixed figure for a given line, when in reality it's dependent on the flow rate.
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