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50/50 is a good mix.
Does it hurt to run bean oil? No. But…Bear in mind that most "bean" oils these days are now a blend.
Straight bean oil does leave a varnish on the hotter areas of the pistons if you are running on the lean (power) side. One of the main reasons bean oil (blend) is one of the oils of choice in racing is that it has a tendency to "run" to a hot spot which aids in protection.
Straight bean oil does not run as clean as a TCW3 oil. Running straight bean oil at the richer ratios that we have a tendency to run and then leaving the engine sit for a season may also allow that oil to get a bit gummy on the rotating parts if using only bean oil instead of a blend of some kind.
Model aircraft engines used to use bean oil plus alcohol and nitromethane for a long time. Those engines were varnished up pretty good when left un-run for a while. They now run much better oils.