afaik, from memory, the record type that you use to script doesn't change, but a separate checkbox + a list/record field will dictate the posting, so that's why I say evaluate based on how much is customized in journals and to what degree you want to achieve your effect

also depending on existing functionality you're using (bundles which might not support multibook) and depends on if you're trying to implement multibook on a pre-established system, or if you are implementing multibook on new subsidiaries I realize sometimes it's a necessity to run multibook for regional, non-IFRS (but legal) entities. Those cases, we implemented fine, we just had to be quite specific to what the new customizations will be. And for the old customizations, what runs for both books, and what doesn't run for both, but only for one. It'll also be more difficult if you run plugin-implementations, those you'd have to look closer case by case basis, just be careful there

And don't forget about consolidated exchange rates, although only the primary book will affect it