Heh, I had this same problem - for about one hour. Once you figure it out you will not be longing for downtube shifters (though I suppose as Patriot says, you may still be reaching for them on occasion).

See if your shop will set you up on a trainer with a bike/set you're interested in and let you loose for a while. If they want your business it doesn't seem like an unreasonable proposition. Bring your checkbook or VISA card