cooking in keyboard SIPs

[bengalih]

Assuming I am starting with a stock ROM, how do I go about cooking in a different default keyboard while keeping all the other SIPs?

I have used SIPChange, but I would rather cook this into my ROM.

I have tried to edit the registry keys of the default KB, but unlike previous posts where the new AKU updates overwrite this info, my device often won't even boot up.

Can someone detail, or point me to a resource that describes the keys and steps I need to take to cook in another keyboard?

BTW, specifically this will probably be PCM, but I assume all SIPs follow the same procedure.

thanks!