Is there a reason that you did not include selection #2 (903.744-926.3232) that is in the MM2-LV-T freewave manual (page 52) in the avaiable radio settings in the CR6 datalogger radio settings menu? Would it likely be included in a future OS update? My understanding is that it can help eliminate interference in locations where multiple freewave networks are in use. Would the notch selection accomplish similar results?
When there are multiple Freewave networks in the same area, the frequency key setting is usually enough to avoid interference.
When you use the Settings Editor tab in Device Configuration Utility, you can access the advanced settings on that Radio tab. The advanced settings allow you to turn off specific frequency bands if you know the frequency of the interference. It is a setting you need to apply to all your radios in the network. A spectrum analyzer can show you which frequencies have strong interference. A standalone RF452 radio with a Freewave diagnostic cable can also show which bands have the strongest signal. (CR6-RF452 does not have the diagnostic port).
Try frequency key first. It is easy and usually does the job.