I've never tried the tuckable holster. I had to find a youtube video to understand how it worked. I guess I could try that.
I have tried an ankle holster. It always ended up resting on my shoe. I guess I have skinny calves and/or ankles. Or a lousy holster.
Locked in a file cabinet is certainly secure and concealed. With my luck something would happen while I'm in the other part of the office.