Gentlemens:
The slot depth is a Catch-22 thing. The trouble is that the plate is only .100" thick. (we experimented with different thicknesses and it was thought that thicker stock made for a less attractive plate.) Therefore counterbores are only .065" deep. It is a pretty fine line between having a slot deep enough to be usable and having enough stock under the slot to hold everything together. This is unavoidably a compromise and there is no complete answer to the problem other than un- or shallow- slotted screws.
Glenn
