The products don't say anything useful except for things like "complies with ASTM 40-D" or "meets or exceeds specifications set forth in DOT-5563 sec. 2" but no where can I find what any of those actually mean * or even how they compare to each other.
So, what I did instead is just get some tape that wasn't too expensive and had a rating from Lab Safety and Supply and tried it out. This is what I got in blue, green, white/silver, yellow, and red.
The photos don't show that the tape really isn't as good as the bandolier I got from motormarket, or the 3M Scotchlite that's on the saddlebags, but it does show that it's still pretty good, especially for $6.20 / 15 feet.
The one on the left is my crappy picture taken with a flash in a dark room. The reflection is strong enough that they appear more white than they really are, especially the yellow. On the right is the photo from the manufacturer, of what it looks like in normal light. It seems pretty accurate.
I did this all the way to the back of the helmet (except for the last few) and then put the second row on. This allowed the intersections to line up so the corners looked right, but it still followed the contours of the helmet. It means the blocks aren't all paralell, but it works anyway. It wouldn't work on a three layer checkerboard I don't think.
For the back I looked at the space left and trimmed the remaining squares so they fit with as little distortion as I could. I was lucky that it worked almost perfectly. The front of the helmet has a square centered, the back has a boundry between squares centered, but you'd never notice that there was a difference without counting.
on the left, in a dark room with a flash, on the right, no flash, in the sun. The reflection from the flash is bright enough that the yellow looses it's color and appears white.
I think the checkers are more noticable than the the solid band I had with the helmet halo. It gives it a British-policeman look I rather like.
I think it looks pretty good, I'm happy with the result.