Recommended distance apart for clip-on bars?

I was wondering if there is any recommended or average distance apart that clip on bars should be from each other? I am referring to the distance where they mount to the handlebar of a road geometry handlebar, not some tri-bar. I realize that user preference will vary, but would like some feedback as it has been a while since I used clip-on bars.

Individual rider comfort is probably the main thing. For most aero position, there is conflicting recommendations from the wind tunnel studies, probably because of differences in individual rider anatomy and position on the bike. Historically, the conventional thinking is narrower elbows is more aerodynamic, but some data supports having the arms more aligned in front of the knees (see pictures of David Millar). Narrower may make handling more difficult.

I would say pick what works best from a comfort/power standpoint.

Thanks! I know that narrow is suppose to be good but I found it to be more unstable that way. That is why I asked. When I was younger, I think I had better balance and that was not so much an issue.

I adjusted mine to the width that does not hinder my breathing. a bit wider but comfortable for me. More feedbacks/experience would be greatly appreciated . Thanks.

I am just not comfortable on mine. I was o.k. when I was younger but now I am not and am afraid I will fall so I think I will take them off for a race this weekend. I might try them on my old bike. I am not worried about hurting myself but do not want to "hurt" my beautiful carbon frame ($$$$$).