Hi Peeps. I need to buy a weed fin and I'm confused by size. Is it true I need to buy a weed fin that's several inches shorter than my standard slalom fin? I assume this is because of the rake measurement from tip to base?

My new 115ltr Tabou Rocket came with a 42" slalom fin. I'll be using sails from 5-7m on it and I weigh in at around 86 kegs hungry. What size weedy should I be looking at buying if I only buy one size (for the moment)?

Thanks in advance.