I've done the handlebar basket for a 15 lb dog. But I have a warning for anyone doing the basket or rear rack and milk crate. You'd better make darn sure they can't jump out. I thought I had my dog's harness secured, only to have her jump to the rear and not the front or side like I was worried about. I was able to stop quickly - but not before she hung upside down and bounced off the rotating front wheel. We got away with a cut leg. But if I had been riding faster - let alone been bombing down hill - it could have been much, much worse. It was a frightening and embarassing incident, both as a cyclist and pet owner. I have since figured how to secure the harness to the bottom of the basket so that she cannot get so much as a leg outboard. Still, I would only consider puting her in there for the most sedate trips.
DanO