Doc,
Imo any mesh that has holes big enough to let enough air through will also let debris through...
get on the blower to K&N.
They sell a thing called a 'pre-charger', designed to keep dust out of their filters.
Buy one of those (pick a suitable one) and then cut discs out of it to replace the foam in the ones you have above.
At least that way you get good airflow, and manage to keep out most of the debris that would otherwise damage your engine.
Just a thought...
K&N PreCharger Filter Wraps, DryCharger Filter Wraps, and Airforce Pre-Cleaners