Re-Raising Standards

I've been recently teaching no limit to some friends of mine, so I'd like to give them a rule of thumb for re-raising. Of course every situation is different etc. etc.

I was thinking that if less than 1/4 of his hand range dominates your hand (pocket pair vs overcards or vica versa don't count) then you should re-raise preflop. This is calculated by looking at the villians pfr, and assume that he raises the best hands.

Example:

You have AQ. The only hands that dominate AQ are AA KK QQ and AK

given you have AQ, an opponent will get one of these four hands about 2% of the time (AA ~.25%, KK ~.5%, QQ ~.25, AK ~1%), so if the villian's pfr is greater than 8% you should re-raise his preflop raises

So, who likes my general approach to re-raising standards preflop? and who likes the specific fraction of about 1/4? I'm thinking maybe 1/5 is better

Btw, this is for 6-max NL, and in my experience position actually doesn't seem too important. If I am re-raising AQ preflop I actually prefer to be OOP so I can bet any flop, and fold to any resistance. In my experience since you will be getting 10%-15% of your stack in preflop initiative seems to be much more important than position

And I'd be very interested if some one thinks there is a better rule of thumb for re-raising