Well if I have calculated this correctly (converting sq cm to sq ft and grams to oz) I have the numbers for 1/64" ply and the kit stock 1/16" balsa sheet weight.

The 1/64" ply has a weight of 4,3 oz/sq.ft.
While 1/16" balsa sheet (stock from this kit) 1,5 oz/sq.ft.
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Conclusion: Balsa sheeting has a third of the weight of 1/64" ply. Approx 1 sq ft is needed to sheet the turtle deck and if using balsa there is 2 oz of weight saving compered to useing thin ply. I am going to use 1/16" balsa sheet for this job (as well as trying to get my little hands on some more contest grade for even more weight savings).