A few improvements over my first version (http://www.thingiverse.com/thing:528775). Now have an even better version (http://www.thingiverse.com/thing:733390) which can support more phones. Works best with a Note4 in an Otter Box enclosure. Works without the enclosure, but may require more adjustments.

1) Added 38mm and 48mm lens holders as an option
2) Increased the clearance around the nose for comfort
3) Increased the surface area for application of 3/4" weather stripping
4) Replaced the top strap fixture with a clip like the sides so you can easily remove the straps for hand-held operation. Now you need to print 3 instead of 2. (Sorry, I didn't touch the original STL so it still only contains 2 - print twice, keep the best 3). No need for supports.

The magnet trigger remains quirky on the GC design. I have found that it seems to work well if, after dragging the magnet to the bottom of the slider, to continue to pull down - rocking the magnet counter-clocwise ~45 degrees.

Update: I found a cheap supplier of nice, large (48mm) lenses: http://www.surplusshed.com/lens.cfm. Pick lens L7315 or L7128 (glass - for $4.50 each!) and print the bigger lens holder. For me, I have these new lenses all the way back at the stops as my eyelashes brush against them. Although it works for me (slightly near-sighted), depending on your prescription, you may not find that is sufficient. Stay tuned, I will likely produce an updated viewer with the phone a little farther away so the lenses can be farther from the eye allowing more flexibility.