but placing your chin all the way down cue can potentially lead to some stroking issues - keeping your head stationary and limiting your follow-through. First, unless you keep your cue absolutely parallel with the table surface throughout the backstroke, your head will likely have to come up some during your backstroke.
Actually and usually, most shots I've seen don't require massive amounts of speed/force. A good nice easy follow through is not hindered by the chin as you are not pressing down on the cue.
As such, when you stroke, the chin does not really limit you or make you or your chin wobble up.
It's just relaxed contact serving as reference point for sighting and stroking.
Also, having the chin on the cue will encourage you to stroke extremely parallel to the table - a big plus usually.
For me nothing is more horrible than the wobbly strokes we see with for example van Boening. Seems also related to the taper of the shafts.
On power shots the contact point of the tip to the CB should be when your arm is at the lowest dead point (+- a bit) and then your arm will complete the circle upwards again for the full follow through. The follow through will end by your hand touching your chest.
Video(s) might be better than explanation:
https://www.youtube.com/watch?v=vxPAhlLOqg0#t=1m15s
Watch for different players and different approaches.
Also moving to a more parallel foot stance helps, too.
From personal experience for a casual player (once a week) using chin contact helped greatly reducing the time needed for "getting used to it all again" and improving long pot chances, reducing unwanted side spin too.
Cheers,
M