"Chris Friesen" wrote in message

Note that you need some space for the air to get *into* the cabinet...at
least as much total area as the dust collection port. The trick is to
have the air coming in through places where there isn't dust trying to
go out.

Yes, you're right, but even a zero clearance insert should allow sufficient
air flow to stream dust into the cabinet and then into the dust collector
port. As well, most saw blades (at least combination blades) have gullets
which also allows a substantial amount of air flow to be directed into the
cabinet.