Surfing Waves

Hey guys, I'm new to this forum. I picked up a horrible rotten mess recently that I just finished cleaning up. It's a 6'6 polyurethane fish with major rot around the fin boxes. After deglassing the fin boxes practically fell out. I removed all the rotten foam away from the boxes and rails but now am left with less material than I expected. I'm considering all options: Microbaloons, Qcell, 4 lb polyurethane pour foam.

What are the pros and cons of each. I obviously need something strong enough for fins.
Thanks guys!!

Cut out the fin area in clean 90 degree angles.
Get a donor board / blank and cut out a matching foam block to fit into the void.
Resin it in.
Shape / sand down the foam to match deck / rail / bottom.

p.s. That's not a fish shape.

My bad, I guess you'd call it a swallowtail

Hahaha most likely most of us would never tackle a job like that. Why not get a new blank? Anyway my thoughts are anything with resin is going to make the board heavier and with the huge defects you have to replace that would alter how the board works significantly. If you have an option to pour new foam that might be the solution however I have never heard of anyone doing that know nothing about the possible problems associated with that. all said and done you will likely end up with a board that would have a significantly shorter lifespan than a new board because you are starting with old foam