think there's a uefa rule that a player has to be at the club for 2 years to be included in the B-List and anyone who has signed more recently has to be fully registered, presumably as a foreign player to play (because they won't have clocked up enough time within scotland to be considered nationally homegrown)
25 man squad consisting of:
Foreign Players: Up to 17
Players Developed Within Nation: 4+
Players Developed Within Club: 4+
Minimum 3 keepers