In answer to the initial question, as a happy Arrow III owner, I don't think that these are difficult machines to convert to at all; In my experience, 5 hrs was more than enough to convert to type and after 30 hrs, I've forgotten that it was ever even an issue.
Having said that, I reckon that you should be completely comfortable with flying, navigating and landing a fixed gear/fixed prop machine (and before anyone asks "why would you even have a licence if you weren't?" - I have met a few fresh PPL's who needed to work at this...) before increasing the work load.
