Hi Isaac

So, I have tried both methods, the first as it has 2 different datums with the rules means that any change in thickness of the materials for the drawer sides moves the hole so i would have to go in and correct every time I use it which is a bit of a pain.

As you said for the second method as you said this is impacted by the drawer clearance, which is less likely to change but then if not done a routine basis would result in changes being forgotten.  

So would prefer the first method due to routine, but if you can think of a another way that we could maybe use the internal zone of the drawer or something like that, but I cannot think of a way of doing that.  My drawers have overpassing sides and the the fronts and backs are rebated into the sides, bases are under passing the sides (grooved)  and overpassing the counter frontage.

If you have any other thoughts please let me know

Thanks

Patrick