we have some dunes here in alaska like nothing you'll find in any other state. the sand is actually silt and the particles are 4 times smaller than the sand grains that you are riding in. long story short....i have the same filter set up as you and the outerwears prefiler blocks 90% of the dirt and the K&N catches the rest. i would say go with the the thin prefilter, you will get alot more power and as far as im concerned be perfectly safe to run in sand.