There's no such thing as a "full vacuum". 100 Pascals is 0.1% of atmospheric pressure at sea level. It's pretty frickin' close to a "full vacuum". If there's a leak anywhere in the tube you're boned.

By full vacuum I was referring to the conditions you have in space. And no - when you have even a slight allowance for a margin of 'error' or leakage - that's all you need to balance things out. And if the leakage is higher, it's a matter of efficiencies reducing - not complete failure.