I think you'd better get to Mangaia! A 99.4% eclipse might give you a little darkening & cooling, but you won't get darkness, corona, 'diamond ring' or any of the other effects associated with totality. The sun will still be bright in the sky throughout, too bright to look at. Think of a 0.6% illuminated lunar crescent - very thin, but you can still see it. That size 'crescent' on the sun would represent a lot of light.
Mind you, I'm no eclipse expert - with a bit of luck, the July 2010 eclipse will be my first 'total', but I'll be a bit east of you. Good luck with it!
Cheers -