Maybe I’m misunderstanding. Are you going to race Cincy? If you’re not racing it, why train for it and why would you think you’re going to “refamiliarize” yourself with the distance by just running it? We could all run 26.2 miles but that’s still worlds different than racing a marathon. If you’re not going to race it, I’d say base building through the winter and spring would be the best way to go.
In fact, if you are going to race it but you are not concerned whether you run 3:40 or 3:50, I might still say simply racing it strictly off base training may be a better choice for your fall goal. Otherwise…
…you are giving yourself only 1.5 months for base training when base training should ideally be at least 3 months long.