One thing that is a side effect of 18 hour callout is that it makes people much less usable following a rotation or SC, so it can be harder to track who on the availability list is actually legal for a particular assignment. It can be done, but you need to dig a little deeper. SC can actually be a beneficial roll of the dice to not get used the following day, or at least not until a very late report. Lots of times scheduling will dump a ton of people with 4 days of availability onto SC on their first day. Then they don't have anyone the following day available for an early report 3 day trip so that gets broken up or sent out as a GS. From what I've seen scheduling generally will not reduce someone's SC period in order to give them an assignment the next day.