RE: natural wood color filet
The answer to your question is use epoxy mixed with West systems #404 Faring filler. It is almost exactly the same color you are looking for and blends in very well. Also extremely light weight ans very easy to sand. Use it for potting the wing as well.
Tom
Sorry I misspoke about the product #. It is #410 This stuff works very well even in faster epoxys.
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410 Microlight™Filler Selection Guide
Filler Buying Guide
403 Microfibers
404 High-Density Filler
405 Filleting Blend
406 Colloidal Silica
407 Low-Density Filler
410 Microlight
410 Microlight™ is the ideal low-density filler for creating a light, easily-worked fairing compound especially suited for fairing large areas. Microlight mixes with greater ease than 407 Low-Density filler or microballoons and is approximately 30% easier to sand. It feathers to a fine edge and is also more economical for large fairing jobs. Not recommended under dark paint or other surfaces subject to high temperatures. Cures to a tan color.