Centre a hole on different plane

Newbie but spent fair bit of time but just seem to struggle on what I guess should be very easy.

Making a wire clip for 2 screws.

Sketched the arch, found that harder than I think I should.
Padded out OK

Move onto the other plane
Want to put 2 holes in for screws, have put the holes in but cannot find a way to constrain so they are centered in each rectangle on each side.
Currently just moved with mouse.

Using external geometry I cannot quite grasp

Tried selecting anything & everything with = & <> etc etc.
center of circle, the outer circle etc.

Think must be something fundamental.
Looks so easy on youtube but never seems to match what I am trying to do.

WireMeshClip2SepHole-Body.3mf (18.0 KB)

I want to be able to adjust dimentions fair bit after so I can test strength after printing & alter as requried.

Thanks I/A