I would just go to the trading outlet and shout for an agetech pcb or the madcatz one that I was talking about. If you’re looking to do a dual boot setup, (ps2/DC) I would suggest you follow this thread. Read the whole thread from front to back so that you have an ideal understanding of the process involved in doing such a mod.
Now for my opinion of what you should do. If the stick is already ps2 compliant I would suggest you order a Total Control Plus converter from ebay. It converts the ps2 stick/controller that you want to use to dreamcast. The only way that a dual pcb mod would be viable is if it was something like ps1/Xbox360, because of the security protocol that the X360 has on it’s controller. The reason being is that there are no converters for the X360 and the ps1 has converters for almost every system out on the market.