Can't speak to the SMD question specifically but I highly recommend the 600
hz roofing filter, if you are a CW op. I just bought an Omni 6+ a few weeks
ago and installed the roofing filter (very easy to do) and I use the filter
all the time. I find it's a great aid in cutting noise as well as QRM. It's
a wonderful addition to an already great rig.
Andy W1AWB