Yuppy said..
Are you crazy macro?
Suggesting under 150l for a beginner board for a 90kg bloke is mad!
Clarence has a point that wide boards are harder to jibe. My 170l starboard go is 90cm wide and it's slow to jibe but still lots of fun!
A centre board is also an advantage to learn on.
The biggest regret I had when I started in 1990 was going to a short board way too early.
Buy a big board to learn on and then sell it.
Get a starboard go 170l
Right . may advice was general, not directly to the guy 100 kg not very sporty, but lazy.
But for young guy wanting to learn windsurfing could work fine, or older but determined.
I am sure that if somebody determined spent all the time wasted on sailing straight for hours , up hauling to do beach starts, water starts and gybing
in adequate shallow water the results could be almost instant.
But most are lazy and think that practicing the same element is boring but sailing straight is fascinating.
This 90 kg guy on relatively small board - 130 L is presented with two option instantly:
learn to put foot in right place on the board and keep balance or fall into water.
Several minutes and should be able to sail - but condition Nr 1 - shallow water to avoid stress of falling into deep water and tiring uphauling. Then wind strong enough to keep balance. How often I see guys trying to learn to sail in no wind at all , when expert may have a problem too stay on the board.
I almost forgotten / lost up hauling skills myself , the same with tacking and I am happy with that. Now on the best way to forgot water start too.
Advantage of package Nr 2 is also a price. Cost of smaller , "difficult" package could be around $400 since bigger beginner pack will cost few thousand dollars only to become complete obsolete when learning curve is finished.