Standard practice in mixing fuels is to blend by volume, not by weight. I expect S&W follows standard practice. I don't know anyone who mixes by weight. It all goes by gallons and ounces of methanol, castor oil, synthetic lube, nitro, other little additives that some mfrs use (anti-foaming, etc.). Plain old methanol and high grade castor oil is all you need, and all that went into early glow fuel mixes. Nitro is nice for a little extra power, better idling. Europeans use little or no nitro, because it's so expensive there. They still have a good time flying. Synthetic is not as gummy as castor, will burn in the combustion process where castor will not. Most engine mfrs like a castor-synthetic blend, anywhere from 10% up to 50% castor, 90% to 50% synthetic, total lube anywhere from 12% for big Supertigres to 20% for breaking in, 15% to 18% after break-in for ABC and ringed two strokes & four strokes. I am not an expert, but this is what I've gathered from my time in the hobby.