Above head as far as I'm aware and he favours one hand swings. I lean towards DBs for one hand swings because of this.
If I'm teaching DB swings I just encourage the learner to swing as high as they find comfortable. Some people go to overhead naturally, some to chest height, some to eye level.
The rationale for reduced gin intake and the knowledge of the perils of alcoholism and attendant metabolic derangement has almost entirely come from physicians and researchers.