Small rigid router - Design advise needed

[EddyCurrent]

Eddie, i believe its the other way around. The pressure in the case should be Negative. Not Positive.

Well like I've said before, people can do what they want, I've worked in industrial electrics all my life and if any panels or switch rooms had been negative pressure they would have failed on a regular basis because of sucking in crap through every little gap. If you've ever worked in a Steel Works you would know what I mean.
If you can be sure the only way in for the air is via the filter then in this case it might be okay.

The very bottom line here for eaxmple;
"The only air introduced into the cabinet is filtered before it enters the Vortex Cooler. Vortex Enclosure Coolers maintain approximately 6” W.C. positive pressure inside the control cabinet."
http://www.vortexair.biz/Cooling/Vor...texcooler.html

Here; http://www.nexflowair.com/panel-cooler.php; "Prevents dirt contamination by keeping enclosure at positive pressure"

And another thing, here in the UK it's not such a problem but in the OP's case where it can get very hot, it's no use blowing hot air into the panel and expecting it to be cooled, at some point a proper cooling system might need to be employed.