subsea, did you bother to read my post on surfboards
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=16632 
Anyway, at 112kg I'd say forget about a 5"5. Especially if you're just getting into it.
And I don't know what your learning curve is but a twintip might be easier to begin with [}:)]
Cheers,
S.