Looks good and will be a handy feature for you. Smart thinking on the zero set up also :2tsup:
You maybe able to sandwich a thin piece of alumium (bent at a right angle) on the back to stop the coolant getting in, as in time it might do damage.
I will one of these days get around to doing my cross slide lock like that :doh: I have a thick backing plate so I am hoping I will be able to mill it out and not have to go right though it.
I am it will give others ideas, so thanks for posting it up.
Dave