Posted for "George Braly" <gwbraly@gami.com>:

 
 Gary,
 
 You have the problem correctly described.
 
 If you can gracefully diffuse the air into the large volume under the cowl
and efficiently convert the dynamic pressure to as close to a full recovery of
static pressure as possible - - then you have a nearly ideal situation.
 
 Eliminating the leaks appeared to be the holy grail for the advocates of the
plenum designs... but if you can eliminate the leaks other ways, and do a
graceful diffuser - - then the closely fitted plenum becomes a significant
liability and not an asset in the overall design.
 
 Regards,  George