I just did a MJ 1200 impeller. It's called a "mesh mod" by reefers if you want to do a search on the term. I poked 2 holes in each blade and tied on 2 layers of black gutter-guard mesh with fishing line. A sound dampening product called Enkamat seems to be the most preferred stuff to use for mesh. Probably just knots of fishing line added to your blades would work really well too.