You are correct that a larger person would require more supplies than a smaller person.

In reading about the Germans as Stalingrad, they commented about how it was the big, strapping soldiers who more rapidly succummed to supply deprivation and cold, while the scrawny little guys fared much better with fewer supplies.

The bigger you are, the more calories your body is used to burning in a day, the faster you are going to go through them. Water will be similar, in that there is more tissue to hydrate, so more water is required.

I am not sure of recommendations for what you should store. You could either come up with a multiplier for the typical recommendations, or you could try tracking your typical intake for a couple weeks and use the average to plan your supplies.

Good luck!

Greg