as a heavyweight, i am off the spectrum in terms of the average windsurfer/person
you on the other hand are off the spectrum in terms of lightweight
they just don't make boards specifically designed for us ...
often i start people much heavier than you with sails in the 5.x range
for you with 60 kilos, and a 5.x sail, you can plane in about 15-16 knots
i will be using that sail in about 25-30 knots = double
you could perhaps start with a sail in the 3.5-4.0 range (lighter and easier)
in terms of volume, the same issue applies
my weight in kilos + some buffer (30-40 liters) means i start on a 150-160 liter board
you based on this idea could start on a 100 liter board, but that does not make sense
those boards are typically wave boards
but 125 liters might do it for you !!
NOT easy - especially if there are NO references in your area
i have written about starting here:
joewindsurfer.blogspot.com/p/how-you-can-start-windsurfing.htmlat that weight are you really young or REALLY lightweight ??
if you are young, you may want to think that one day you will be heavier ...
and not go too small