If you could get it to make contact, it would probably light but I would bet the charted curve would be poor and running in direct (and weak) drive the whole time. This light is made for 2 RCR123's, not a single, 3.7v cell.
I could not get my Wolf Eyes LRB168B to work due to the flat top. I have no other 17670s to try. I have a magnet that would work but when I looked in the light, it appeared that if the magnet wasn't perfectly centered, it might contact some other metal I saw up there.
If you want a good single 17670 light that is similar, look at the Wolf Eyes Champion. I did a
comparison review of these two lights last year.