Yes the balsa is to reduce flex being between two carbon sheets, the hand launch guys are using very thin
open weave carbon over balsa and foam. When epoxy bagged it's very strong for the weight. There are different
grades of ply Midwest for me is the best. I am currently framing up my sponsons with 3/32 ply from Finland it seems
softer and heavy. Midwest feels harder, better glue, compressed and cured with care allowing for thinner ply choice.