Rainbows don't require a school like tetras and other things. They'll do fine in a pair. I have a pair of dwarfs in my 55g tank and they are perfectly happy.
Sorry, but I couldn't disagree more. Rainbows have such a high schooling drive that they will try schooling with other species if there aren't enough of their own. Just because your pair hasn't died doesn't mean they are happy. Once you've kept a large school of rainbows, you would never consider getting just 2.
The blue eye rainbows are definitely the best choice for a 29 gallon tank, whether it be furcatas, threadfins, celebes, etc.