TW 10.5 arm overhang set up?

The main advantage provided by the mirror on a Mint or Wally is not the ability to see the stylus. I can see the stylus just fine too, my myopia is well known!

The advantage of using a mirrored protractor is that it enables parallax, which allows you to:
1. move your head to center the printed/scribed alignment grid on the top surface above its reflection off the bottom surface, thus ensuring that you're sighting directly along the centerline of the grid; and
2. with the stylus on the null point, adjust the cantilever zenith angle such that the cantilever precisely occludes its own reflection, thus ensuring that you're sighting directly along the centerline of the cantilever whilst it's centered on the null point and parallel with the grid.

You can't equalize/null the differential between two images unless you have two images. On card stock, there's no way of verifying that you're sighting directly down the center of the alignment grid *or* the cantilever.

Imagine trying to focus a split-image rangefinder lens without using the split image. All you could go by is the apparent sharpness of the image. You'd probably get close but you couldn't match the precision of matching split images.

Perhaps you're not using your Wally to full advantage?

Doug,
You clarified that better than I ever could have.
The mirror is so important for those micro alignment adjustments. It's just not possible without it. Once you have a Mint or Wally (and use it to its fullest advantage) you will see (and hear) this for yourself.

I agree but there is a line on the protractor that needs to align with the stylus. It isn't as good but it s very close.

O will admit I am a VTA/VTF believer over HTA. I hear it much more and measurements seem to agree with me.

...I am a VTA/VTF believer over HTA. I hear it much more...

Fair enough, so do I in some cases. Of course this is cartridge-, system- and listener-dependent.

Another use for a Mint or Wally is setting initial azimuth. That squared-up view of the grid, cantilever and their reflections makes it easy to verify that the stylus is oriented precisely to the vertical. When the stylus and its reflection form a perfect "X", azimuth is very close. Fine tuning from there while listening is easier, faster and more enjoyable than fussing with a Fozgometer, Wally Analog Shop, ocilloscope or voltage meter (unless you prefer fiddling to music, lol).

I get a lot of mileage out of this $100 tool. The Mint and a VTF scale are the only measuring devices I use when setting up a cartridge, typically in 30 minutes or so. I can't do it so confidently with any of the lesser protractors. Of course YMMV!