RE: How close is too close?
Well, how good of friends are you with your neighbor? Theres no law against putting a stand too close to another person's stand (that I know ) but it may piss some people off.
Can you see his stand from where you would put yours? Would walking to your stand interrupt his hunting? I would take these in consideration.
Or, maybe you could just ask him. Some people don't fret over things like this.
Good luck!