What size board is best

Hi all
New to this site and I am going to start my board soon.
I have a old school dona windsurf board I’m going to cut to size any recommendations on size I should do

my opinion is to leave the board length between 155 to 180 cm and displacement around 65 to 80 liters. But everyone will tell you something else. Boys here also have surfboards with a displacement of about 20 liters but over 115 liters. I have a length of my surf board 156 cm and a displacement of about 65 liters (estimated)
Original dimensions 255 length, width max 63 cm and displacement 101 liters.
I would probably choose a length of about 170 cm today. Your body weight is important. I weigh 93 kg.
Wide surf is preferable (has a larger displacement at a shorter length)