Refer to CBA 25.D.1.a-e, and 25.D.2.a-e. A couple things. The CBA allows for a 13 hour split between low and high line. The second section allows that VTOs be build with the same rules as regular lines, except that 'R' days may be used. Both stipulate CBA compliance, with min days off, 4-3-2, or 4-3-3-2 blocks of days off, etc. So, as long as your 58 hour BLG is within 13 hours of the high line, I'd say it's legal. As long as the Company is using 4.A.2.b to do their alleged manning mitigation exercise, I think we can expect just about anything.