Thanks! Exactly the kind of info i was looking for. :smiley_thI bought a 90 degree extension from this on-line vendor...
no relation, no previous affiliation. Not only did they have the best price I could find at the time, but they shipped same-day and it arrived fast. It works great. I don't leave it on the tires because I read somewhere it could throw the balance off. I keep it in the saddle bag and screw it on when I need to check pressure or add air.
When I eventually need new tires, I will have a permanent 90 deg valves installed.