I have a breeding pair in my 29G Breeder just for a month or so now being that they kept fighting with their tank mates and making their life miserable.
BUT I have 2 Angels in my 72G tank and they are as big as my hand - medium F sized, and extra long pectoral fins, maybe 9" long fins, the fish is half the height of my 72G tank, they really swim a lot and the amount of space I think they should have would be 4 foot long tank for swimming.
My breeding pair is a bit smaller that the other ones - they used to all live in the same tank.
In a 29G they probably will not grow to their full grandeur, and really not have that much room to swim, just kind of wander around.
If you decide to do them in a 29G I might only do one, and i would hope you do good sized pwc
every week and not overstock the tank for the best results.