-Group size is entirely dependent on the type of area you are in. In an urban environment it would be much easier to conceal resupply of a large group than in a relatively rural area (this is assuming you don't have full control and civilian support). I would say, however, that whatever you do you want to have at least a secondary, and possibly tertiary, position already set up. The standard operating procedure of most militaries the past seventy or eighty years is to take out lines of communication and resupply. After all, it doesn't matter how motivated someone is if they can't get beans, bullets, and backup when they need them. For that matter, you might even want to consider investing in construction of what appears to be a central supply warehouse for the express purpose of allowing it to be eliminated. This would serve two purposes. One, ambush; and two, misdirection. If they are convinced you lost your main stockpile, they'll be sure you will fall in a short time and plan for a completely different style of warfare.