Once you extend far forward you may need to move the seat back a bit to avoid too much weight on your hands, especially if the bike has steepter seat tube angle (ex: 72 degrees). I agree with the previous remark about having one's arms bent being desirable, but one needs not to feel cramped, especially on turns, and too short a reach with long arms can put excess weight on the saddle as well as force a more upright position.

KOPS, incidentally is Knee Over Pedal Axle, the idea that with the crank level and forward your knee joint should be directly over the pedal shaft. Google it if you want the whole story, but I'll say straight out you should not worry about it, as the main concern is putting your seat too far forward, and as noted about I think that's unlikely.