15" deep is the minimum recommended overhang for counter-height seating - for a reason! Skimping means you don't have enough room for seating in your kitchen and your guests will not be comfortable sitting there for very long.
If you don't want guests sitting at the counter, then skimping on your overhang may be the answer to keeping them away! (only half in jest...)
Kitchen Design FAQ thread: Aisle widths, walkways, seating overhangs, work and landing space, and others
http://ths.gardenweb.com/discussions/3638304/faq-aisle-widths-walkways-seating-overhangs-work-landing-space-etc
.
Q