Thats what, 5 months? Check to see how fast they grow. If its 2" now then its fine in a 29- but if its gonna get to 6" by the summer then i dont know....
It prolly wont grow that fast though so i would say yes. But check it out first though.
I think that it'll be pushing it. Flowerhorns, I believe, grow just as fast as any other large cichlid with proper care and nutrition, but I think you should be okay until then.