You could speak to the realms' banker about all that. I know how many days' supply of food we have, and I have ideas about how many warehouses we need and where they go, etc.
All you, as lord of a food-deficit region, need to know is how much food you have, and is there enough food for sale on the markets within 400 miles of you to supply your needs. I think you should build enough granaries to store 30-60 days of food. Beyond that, don't worry about it.
Relying on others to get the job done has had disastrous results in the past. I'm not a fan of leaving critical operations entirely to third parties.
With 6 granaries, I can survive for about 46 days...
So, is it me or do I know less than before about my duchy? I used to know the consumption and production rates of all regions in my duchy. Only the banker knows this now?
Personally, I'd rather have enough granaries to last 84 days.
Damn Allison can't mind her own business...