To be very rigorous, you should detect select valid packet with
in the packet header :
id: service = 3
id: subservice = 25
in the packet itself 
id: sid = 6
The CRC is checked by the AX-25 routine ???
I dindn’t understand how the frame decoding is performed ?? Is it done localy by the satnogs client ? Or on the satnog server … I checked the audio file in the server (oog files) and the audio bandwith is near 8kHz … it is too narrow to demodulate a 9600 BPSK signal …