I ended up doing this by using the BeforeTimeHeaderRenderEvent
if (!e.IsColGroup)
{
string hour = "";
if (e.Start.Minute == 0)
hour = e.Start.Hour.ToString();
e.InnerHTML = String.Format("<div >{1}</div><br/><span style='color:gray; font-size:8pt'>{0}</span>", e.InnerHTML, hour);
}
with the scheduler settings
CellDuration="30" and CellGroupBy="Day"
Maybe this will give someone some ideas.