I have used the Klingspor 80 grit VD6001 & 120 grit VD6003 disks for epoxy fairing work. These are the PS33 disks, and work far better than the Makita or Norton disks that I used previously. They also seem like they last quite a bit longer and remove material more aggressively for a given grit.

You can also extend the life of the sandpaper by hooking your ROS to a wet-dry vacuum. Greatly reduced airborne dust, no fiberglass itching, and longer disk life. The dust removal on my Makita never quite kept up with the amount of material removed by the sander. This resulted in the sander 'floating' on a bet of epoxy dust. Get rid of the dust, and your sandpaper does what you want it to do - sand your boat.