Quote Originally Posted by Monty3038
Another way of narrowing their range is to use their VPIP and PFR stats... though I rely on it others warn me not to.
I'd say given enough hands against an opponent, they can be reliable. As long as you have some showdown info to back it up as 20% may not be the top 20% of hands. Also, position will matter as 20% isn't 20% from all positions (as you mentioned).

And to add to the raise vs call, a reraise can help narrow even further.