it has been some time, however I had a set that were very hazy with surface hairline cracks. I started with 800 grit and got no where. Started again with 320 and sanded aggressively using a DA/ Dry. Canopy turned "white" and I removed a lot of material. Thought I ruined the canopy, but I worked my way up to 1000 and the canopies came out great and very clear
A work of caution - too much time in one spot will create a "lens" and even though it is clear you may have a spot that is magnified. Keep you sanding tools moving.