Yes, there is a rule. Put it where you can see it. Take a small refrigerator magnet, put it on the barrel, put the sight on, slide the sight & magnet back & forth to where you can see it clearly, then slide it 1" forward of the place & that is where ya put it.
I never worry about where my hand is going to carry the rifle, in regards to the sight being in the way. Regardless of where it was, it has never bothered me as my hands are tough a leather. I can easily move my hand fore or aft of the sight & be comfortable. Also, it is not like I am going to trek all day with it. When I hunt I do allot of standing & sitting, and when doing so, I usually have the rifle in both hands.....
Now the ideal place would for or aft of the balance point, but I have always put it where I need it to sight it well. I would be pretty upset to have a huge 12 point looking at me 60 yards away & I can't see the dang sight ...... :cursing:
Keith Lisle