roof vent

[Bob Haskell <rchaskell@earthlink.net>]

Listers,

I'm going to be modifying a hardtop for some additional head room.  While I'm 
at 
it, I was wondering how effective the roof vent (as fitted to the works rallye 
cars) was at improving the ventilation.  Has anyone started reproducing them? 
I've looked at a couple of Healey vendor web sites, but didn't run across any. 
There's always ebay ...

Thanks,

Bob