I agree with @Tim that figuring out where the emphasis falls is definitely key. The other key question is what is supposed to come after those 29 notes — maybe there is a plausible remainder of the 3rd measure. Or maybe the first 5 triplets were an anacrusis to the first measure?
The kind of music I can think of where 29 triplets could constitute a complete section of a song would be Eastern European or Middle Eastern folk dances, where people settle for odd meters as a rough approximation of the true underlying pulse.
So if you are e.g. an Armenian Jazz composer, feel free to write a measure in 29/12th time. If you see yourself in more of a traditional Western European tradition, odds are that your melody in reality has a more conventional rhythmic arrangement, and just just have not quite found the right groove for it yet.