I busted mine up a couple times on my cub and ended up making a couple out of that brown stuff that a clip board is made of. Hold tough but still breaks like you want it to if you nose in. I’ve proved the concept accidentally.
I use AC grade 3/32" plywood for general use (1/8" is ok but a bit heavy) (1/16" is ok for small minis) I purchase from a hobby stores and you can find pywood at a craft store such as Johanns (sp). You can also go online and find many supplier to AC grade Plywood. As said, balsa not good. Nor is what they call "Lite Ply" it is to weak and will fail. However, for me is, to order flyer walls from Flite Test.