If you are shooting 6x9, I would strongly consider a Leica 12011 Universal Wideangle Finder M. It has projected(!) framelines for 16 (=35mm), 18 (=38mm), 21 (=45/47mm), 24 (=55/58mm), and 28mm lenses (=65mm), which correspond to the Horseman focal lengths. It has a parallax corrector for various distances and a top-mount bubble level. I like it a lot better than the Horseman finder (though to be honest, I have had this thing for a week, so no hardened opinions quite yet). Funny thing is that I never used that finder on an actual Leica in all these years...
The Horseman is considerably fatter than expected, and although the shutter release and winding are convenient compared to most similar cameras, it's no Brooks Veriwide 100 in therms of overall ease of handling.
I also feel like the SW612 scrimped a bit on accessory shoes; it would be nice to have a 4-way level and possibly a rangefinder!