I have been running very tight 500Hz receive filters and for the most part they have been working great. However I realized that some stations are off my freq by 50-80Hz and the link becomes a problem as they are now getting one side of the spectrum cut-off. For stations that are off that far I have to run 600Hz filters.
Most stations I work have an AFC correction of no more than 2Hz but there have been a few stations that are in the 50-80Hz range on the AFC meter.
500Hz filter:
600Hz filter:
I always use 600 on my Flex and it seems to work well. I figured that some stations might be off-freq, so 500 would just be too tight. I also rolled off the filter sharpness.