The mounting slide of the Maestro and Oboe has three holes to fix it to the body.
The upper two mostly coincide with the measurements of most Clarinets and Oboe's.
If not, one or two new holes have to be made at least.
But a third hole is always necessary to obtian a good solid fixation of the mounting slide.
It is not a problem at all doing this.
I have drilled thousands of holes and the little holes alway can be filled practically invisible in case an instrument has te be sold without.....
Drilling is done by hand by means of a hand vice and can thus be done very safely.
Drill and screw one after another to prevent the mounting slide to shift.