I think Irvin is right, I don't see how your formula can account for mass distribution if you're only taking a static measurement. Your numbers can be in the ballpark for most rackets, but the more extreme the setup, the more you'll be off.
Consider this : if you were to take 2 identical...
I think string spacing should definitely be taken into account when deciding what tension to apply to which string. Which means there isn't a single proportional recipe that works the same for every racquet.
1 : If you're pulling 60 pounds on 2 strings at once, you're getting 30 pounds on each.
2 : I think you might be getting about half the tension on the string you're not directly pulling, but definitely not the full tension.
3 : I sometimes pluck the mains, but mostly i don't. Pushing on the...
If I had to guess, the difference comes from how long the string is under tension before clamping, but that is the same with any constant pull machine. The longer you wait before clamping, the tighter the string job will be.
12 meters is long enough to string 2 piece. You can make do with a little less (how much less depends on tension and stretchiness of the string) and 1 piece uses a bit less, since you have only 2 tails instead of 4.
If you string 1 piece, you get 2 knots (one at each end) and same if you string 2 piece, you end up with 4 knots. "2 piece" and "4 knots" mean the same thing, unless your stringer has gone crazy from huffing too much paint and somehow adds unnecessary knots ^^'
The important part of what Irvin said is "you should try changing only 1 thing" ;)
That's the interest of trying your usual tension with a 4 knots pattern, that way you can compare 1 piece with 2 piece, and you know any difference only comes from the pattern, not from the tension.
In the same...
I'm not sure what you hope to achieve by clamping the string as soon as possible, whether you lose tension before or after the string is clamped, the absence of constant pull means you'll lose tension either way. I'd also advise to pull at a slow consistent pace to minimize this tension loss.