Peter,
Firstly, a warm welcome to Eratosphere, and especially to D & A.
There are no hard and fast rules, as such, for The Speccie comp (apart from 16 lines max and keeping to the theme), though to "re-write" a poem would seem to indicate that a parody is called for, in my opinion. But you don't necessarily
have to keep to the original rhyme scheme!
I would suggest that you submit your Killarney entry as it is; you can always offer Lucy an alternative version as well
Good luck.
Jayne