With a lot of new H3 owners posting, I thought I'd repost this economical low tech solution to H3's limited rear visibility. I've had one of these fresnel-type fisheye lenses (5x7) on the rear window for a few months and it's a great vision enhancement
once you get used to it. I simply want to know if there's anything behind me and this lens shows me. It doesn't even use adhesive, it sticks on the glass via suction (mine shows no sign of slippage). The link below is just one source but is a little pricey. I found mine on eBay for $15.
http://www.rearlens.com/