WAY back we used a 24-1 ratio of 30 wt motor oil to leaded gas in those old 2 hose engines. (A full quart of motor oil to a 6 gallon tank of fuel). Todays 2 stroke oils are far more refined and do a better job of lubricating. One thing different about the oil today is it's ashless and does not leave an ash or harmful deposit in ring lands etc. It's designed for lubrication but not to burn up in the power stroke. Yes, it does burn off other wise the engine would be all carboned up but viscosity is such that the cyl walls are lubricated better and the lubrication lasts longer. Again; it doesn't burn off as fast leaving a film of oil on the pistons and cylinder walls.
I personally believe you should use 50-1 in your 60's double hose motor. However, to be safe, use the newer 50-1 oils in a 25-1 ratio. Either way I think you'd be more than safe. Just be sure to use quality name brand oil.
Same thing goes for the synthetic oils. Some companies suggest going to a 100-1 mix where 50-1 is standard. Double it and you're good to go. In your case, mix 24-1 and be over cautious. Expect a mosquito slick to follow you but there shouldn't be any lubrication issues.