Blue foam covered in brown paper is worth a try. Lighter stronger much cheaper than balsa and much easier to repair. I build wings this way up to 45" with .32 engines.

There is a kit for a 4 engine Lancaster of 8 foot span that blue foam and paper. Flies eally well on 4 x .15 Sc engines.

We fly 12th scale combat and I have wings that are 3 seasons old and still good.