There's a property called HourLineColor to change the color of the line, but that line it's not even shown where there are enough items. It would be great to have a property like HourLineGap (space before and after the line).
It might be visually useful for some users if we could separate the items from one hour to the following hour. In some cases, there are items every 5 minutes and when it's all occupied the user can't distinguish between one hour or the other (we show a week day for every position).