What is the range of magnification/diopter strength that would be useful for a 6x9 ground glass for focusing

I'm looking into getting a necklace with a magnifier to be used for focusing a 6x9 ground glass. What magnification strength would be most useful? I have decent eyesight.

So far I've noted:

A typical TLR magnifier is 3x, so I probably want more than that - at what point does the magnification become too much?

I want to be pretty close to the ground glass when I use it in order to block stray light from dulling the image

I might want something all-purpose that doesn't need to be touched to the ground glass and which can be worn comfortably all day

Not sure how practical these things are, but would something like this with a strength of 20x even be useful for the purpose?

Hi,

I like loupes in the 6x (1930s Zeiss) to 8x (1990s Docter) range best here.

Maybe for 13x18cm (once the camera is complete) even the 5x Emo Macromax as the camera has a larger focussing hood...

4x; 6x at most. Too strong of magnification causes too much distraction as the grain of the gg becomes the focus rather than the image. More is not better. Trust the conventional and time-honored wisdom. Or try it yourself and see what works best for you. The one I’ve come to like is the recent offering from eTone. About $100 and well worth it. There are more affordable options to explore what strength magnification works for you. Drug store magnifying glasses are often suggested and that make sense.