Findabair makes me think "find a bear." Not that there's anything wrong with that, but it's hard to avoid!
Finnabair might be a little more user-friendly, for that reason.
And Finna might be a nice nickname for a girl.
Being someone from the west side of 'the Pond,' I have to say it seems like a mouthful I'm not sure I understand the appeal. If you have a simple and common last name, though, it might be worth serious consideration.
(My name list:
http://www.babynames.com/namelist/9516801)