Interesting. I estimated that the handle length, based on the model, is about 1/5 of the gun length. Taking the ratio and my palm width, I came up with 19.9 cm for its assembled height, which is pretty darn close to the value that I set earlier (20.1 cm). I'll set it at 20.1 cm for those with wider palm widths, not that 0.2 cm is going to make that much of a difference.
Thanks!