Peter,
It’s a sheer coincidence, but I have some recent experience with these. The short story - I mistakenly marked the lower two holes too far down and then drilled them. The bottom of the tuners I had planned to use hit the volute as a result. I noticed these economy tuners had less material below the post and would just barely fit so I replaced the buttons with white ones and went for it.
I also noticed they were stiff at first but having wound two sets of strings on them they loosened and feel fine now. Hope that helps.
Here’s a pic:
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