i am about 6'1" tall and 210 pounds
today i was out with a longboard and an 8.4 in about 12 knot winds
i have used a 10-oh and 94 cm wide freeformula in the same winds
i rarely use a 6-oh now ...
in other words - if you are strong enough do not start with anything under 7-oh
my most used sail is 8.x, but that would be difficult to start with
80 cm waves are pretty big in my book - i sail inland lakes and rivers
i have no experience with RIO nor GO
i do know that people speak about Fanatic Vipers as great first boards - sorry SB
some say the KONA ONE is an option, but i am NOT so sure ...
hope others chime in with more personal experiences
i started with a BIC Dufour WIng many years ago and people strongly suggest against that now - with all the better starter boards available
hope you find something that works for you NOT too expensive and you stick it out !!!
i have become a fanatic and now windsurf 60 times a summer and about 40 in the winter on ice and snow on sleds that i built myself :-)
it is a GREAT sport that encourages outdoor activity and forces one to think/eat healthy
GOOD LUCK !!!!
go take more lessons ?? rent stuff ???
talk to the locals ???