Sorry if this is getting off-topic, but:
1. Are ERTO 406 wheels available in "skinny" variants?
2. If so, would they give similiar speed benefits as the skinny 451 tires? and
3. Is the availability of different "skinny" 406 tires better than 451's?
Finally, if yes to all of the above,
4. Why the preference of some people for 451 tires? I wasn't measuring them specifically or inspecting the tire markings, but when I went on the folding bike ride up in NYC it seemed that a sizeable number of the more expensive 20" folders used the skinny (I think) 451 wheels.