The temp fix for the 300XL was to use com2 configured NMEA 0183 (listed as mapping output in the 300XL) sent to com0 in the AFS then used it as the third nav source. This will do until the new puck is available.
The Apollo SL30 appears to be an incompatibility between SL30 software versions. Apollo SL30's expects $PMRRC messages for the com commands while it appears that the AFS is sending a new Garmin specific message ($GPRMC)? . AFS still sends the $PMRRV messages for the nav. I think this explains the COM NG while the NAV works in my installation.
No way to get legacy SL30's to work? The Garmin cost to upgrade an SL30 is as much as some new radios!