Aluminum or steel screen door mesh hung on the outside for easy cleaning. Flail mower might be less turbulent. Do you irrigate, then mow when wet or after a rain shower.
Are you mowing between rows of Pine (Christmas) trees or mowing the trees. Not familiar with a pine 'orchard' in Oregon.
Dennis
You might google 'tire groover tool' as an option to buying new R4 tires if you still have plenty of tread on those turf tires. I cross grooved a set of ribbed implement flotation tires I used for jeeping in the sand dunes.
Dennis