Just unboxed a new Leopold FC660C (Topre 45gm, unprinted 66-key mini). Fits RIGHT on top of my Mac Book Pro Retina; only needed to switch caps-lock and control ('cause of emacs) and I'm in love again. It's smaller than my Realforce boards, but has the same switches, which I like a tiny bit better than the Cherry Browns and Blues (but I love those too!). I like my Happy Hacker Pro2 also, but it doesn't fit cleanly on top of the MBP keyboard without nano-positioning, and, unless I'm living in emacs, having to press "function" to get (the annoyingly necessary) arrow keys is slightly annoying.
Ok, I know I am splitting hairs about which perfection is a better perfection. All four of the above-mentioned boards are 0.01-percenters
But this new one is tops by a hair.