Looking forward to reading more feedback, particularly for anyone who rides a 5'10". I have Mollusk store credit to spend and am thinking I should use it on one of those. I dig how Burch rides one in Temporal Collections and think I could make it work in my local waves:
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How wide is your Burrito's tail? I've got a Baby V with a 16 3/8" tail, and found 9" narrow L-Flex, positioned forward of side bites' leading edge, to work well. About 1" from the front of the fin box. Putting center fin forward of side fins for 2+1 hulls was mentioned in other threads that I dug up (https://www.swaylocks.com/comment/230282#comment-230282, https://jamboards.com/threads/fin-question-for-you-hull-heads.10765/#post-212323).I typically ride the shaper's fin or what they tell me to put in a board, but I have owned a variety of A-Flex or L-Flex fins, or ones inspired by those templates in 8-9" (I've liked a MOTE/Needessentials fin that looks like a wide L-Flex). I also have an 8" 4A to mix things up.
This board is interesting because Andreini's 1/3 of the fin hanging off the rail recommendation does not work with the wide tail of the burrito. I'm about to try a 9" L-Flex and will report how it goes.