as jervin says - your weight is an important factor
winds are obviously important
and location - waves, currents, etc
if you sail in very light winds - older longboards can be a BLAST
under 20 kph i still use a Mistral Equipe I and a Fanatic Ultra CAT - both about 220 liters
like the Viper you tried
however, they are narrower and glide really WELL
at 220 pounds/100 kilos my first shortboard was a 160 liter 268 cm x 79 cm wide
this was and is a great floater !! started with a 7-oh sail and once confident, purchased an 8.5
not planing until using the 8.5, butt was ready for it
as a "learner" length and width are your friends
newer boards are tending to be shorter - however wide is coming back - YEAH
longer fins like 48 cm work great with 8.5 and get you home
there is an F2 Xantos for sale - says it may have some nose dings, cannot see it in photos
take your weight and add 60 to the kilos for your first shortboard
start with the smaller sail until you feel comfortable
see if you cannot continue to beg, borrow, loan , rent until you have a GOOD idea of what works for you
heard JP Funster is a NO GO - X-Cite Ride - YES
have no info on the GO
if you were in Montreal you could try my longboard, shortboard and i have some snow n ice sleds too
recently let a "kid" on an original Windsurfer try my Mistral Equipe with HotSailsMaui SuperFreak 8.5
he had NO trouble getting going and LOVED it !!!
he was lighter and managed in 20 to 40 kph winds - good on him !!!
NEVER GIVE UP = just keep at it
that's what we LOVE about windsurfing !!!