I am 5.8ft and around 150 pounds. I surf in the Med with a freeride board
134 lt in wind speeds between 13 and 20 knotts. My sails are 5.7, 6.4, and 7.
I want to buy a slalom board for the flat water days and I am thinking of
getting last year's iSonic. My problem is which board to choose between the
111 lt and the 122 lt.
I have never used a slalom board before and I wonder whether it's a bad
choice to go straight to the 111 lt, as the 122 lt is 3 cm longer and 6.5 wider.
If you are proficient with your waterstarts and can make 40% or more of your jibes, then the 111 ltr should work well for you. It will also be a bit better on the days that the wind is at or above 20kts.
If your average winds are on the lighter side of the range you speak of, then consider the 122 ltr as it will work a bit better for the 13-15 kt range.
Hope this helps.
Keep on sailing,