Talk directly to your NAA. There may be an "Alt Moc" available which will inform you how to do so. It is possible for instance in a King Air to operate multi-crew under a recognised multi-crew programme (i.e. your NAA must have a document regarding such a programme) Those hours can be counted towards the requirement to unfreeze an ATPL although the skill test must be performed in a transport category aeroplane. Good luck!