I have had a couple sprout keikis from the top of the bulb like CMB mentioned, they were both bulbs that were damaged and broke off the plant during transplant so you could try the backbulb method and also put some keiki paste on it and you might end up with the best of both worlds :D

Blow. I have an oncidium ('Munsterland Stern', which is not a registered grex...) which I was going to take to my orchid society auction in Jan to make some space. I might have to keep it now. It has three pulbs one on top of the other!