I don't think it's too bad, myself. I guess because "undone" has two sylables. Like, ended and suspended. I worked to see if I (perish the thought) could come up with anything better that kept the meaning and all I came up with is this: Your travelin' days aren't through Though fiery feathers earthward fell; Like waxen wings unglued. Even that doesn't seem as good to me. Besides the "near" rhyming of the two words in question, there is the "follow-through" problem with using "through" and the next line starting with "though". So, I think the "done twins" are the better choice. PS, pardon me for being dumb, but all I can't think about is Sally Ride. Does it have anything to do with that?