This is the applicable part of the CBA

"Section 24 E. 1.

b. Down/Lateral Bid Restriction

Unless waived by the Vice President, Flight Operations, or his designee, a pilot may not receive a permanent vacancy award based on a down/lateral bid unless he has been in his current crew status for at least 18 months.

c. Down/Lateral Bid Freeze

A pilot who is activated in a crew status that requires ITU training based on a down/lateral bid shall be frozen in that crew status for 24 months, commencing on his actual activation date. A pilot is not eligible for a permanent crew position award requiring ITU training with a projected training date during that freeze period except under the following conditions:

i. the pilot was excessed or down/lateral bid to relieve an excess; or

ii. the pilot down bid because of legal restrictions."

So, as I read it, you must be on the 72 for 18 months before being awarded the same seat on the 75. However, if you were awarded the seat on the just completed posting, you either have the time, or it was waived by VP Flt Ops. Once activated, you will have a 24 month freeze if the assignment was a lateral or downbid, although being in an FDA and signing the Letter of Aggreement makes the freeze problematic, as you'll be there at least 24 months.