According the manual the holes of the trim servo should be enlarged to accommodate a M3 rivnut, but that leaves only 2 mm edge distance.
According the manual of the Ray Allen servo the holes required for the M3 rivnuts are larger than allowed.
With the solution below the holes were enlarged with a #27 drill.
I fabricated 2 small aluminum strips with anchor nuts:
Ready for assembly:
Inside view:
Outside view:
