Strange someone should mention upside down shocks, as I actually came across this today doing some background reading, and in the damper section it mentioned them as being fitted 'upside down' compared to R/C stuff, took me 2-3 times reading it to realise I was reading it correctly after all
as for performance reasons, I'm not entirely sure, it could be that it's easier to direct airflow onto them for heat dissipation when they're 'upside down' in saloon and open wheel cars, but that's the only reason I can think of
edit: as to what northy said, i think that's a design point for the progressive damping, as in if you had the exact same damper, reversed the valving on it, and put it on the other way up it would work in the same way... but not sure on that, that's just how i understand what i've read
