Are you talking asbout the faction capitol Id? If this is the case you should enter there the Id of Maryland.
Now for the rest it is not hard since you are familiar in hybrid method, but you need to go one step back. When you buy Maryland and US is fully playable, save, exit game but do not make hybrid. Open save game go in REGION maryland and in minor building slot change minor_magistrate to minor_governors_barracks. In this way you'll have better choises in units. Now start the game and load the saved game. Recruit the units you want included in your starting army. Play the turn. If nothing major has happened (e.g. be attacked), save game and exit.
Now you can make hybrid but except tresuries you have to make some more corrections. If you want to change the building you know now the drll. You can find the building names in patch.pack db/building_levels. Then go in [...]CAMPAIGN_MODEL/CAMPAIGN_CALENDAR and replace 1 (turns that have been played) with 0 in 2nd and 3rd line. Then go further in DATE and replace winter with summer.
This tutorial will help you convert Maryland to 5 slot major city. You can downgrade Pennsy in this case.