Looks like 0.525" deep is a nice balance between coil bind at 0.420" and free assembly length of 0.595". I also decided to drill 0.145" off center-line of the button, 0.160" just seemed too shallow of an engagement. The depth allows for the detent to be set flush with the frame surface as suggested by Fastbolt in the next post. I did have to take a thread off the mag catch as it was proud of the button in this configuration.

No more plastic (ok, save for the grips) on this CS45!