According to the bought plans the wing should be skinned with 1/8" (3.175mm) Mahahoni plywood. It is hard and expensive to source this kind of plywood in Europe. So I was considering from the beginning to substitute the Mahagoni plywood with finnish aircraft birch plywood, either 2.50 mm or 3.00mm thickness. To compare all three materials I make samples wich were tested to destruction in a technical laboratory. The results were surprising: The Mahagoni plywood was the weakest, even the 2.50 mm birch plywood is stronger to compression by the factor of 2.5 compared to Mahagoni! On the downside I have to note, that the mass of 2.50 mm birch plywood is 7% higher than Mahagoni plywood.