"You really do need to be careful with the overlap; even 1 pixel of overlap can throw your performance out the window."

This brings up a question I have had since I tried to use the 3 client maximizer layout through keyclone. I noticed that all of the layouts do not overlap and it got me asking why? I have been 2 or (now 3) boxing for over a year with major overlap on all three clients. (2 slaves stacked up on the left side of the screen, the main overlapping all except the last few inches of screen on the left side.)

What performance issues should I be experiencing with my screen set up like this?