I just configured mine to emit an ICAO code of 40526F
But this is what was produced and sent to the OGN
SKY475048>OGNSKY,qAS,SafeSky:/192459h5223.53N/00127.45W'245/000/A=000239 !W42! id20475048 +000fpm gps17x6
I then changed to 444444, and it produced
SKY7F411F>OGNSKY,qAS,SafeSky:/193159h5223.53N/00127.45W'235/000/A=000239 !W31! id207F411F +000fpm gps5x3
I entered your code 40651B, and I got
SKY47CF4B>OGNSKY,qAS,SafeSky:/193338h5223.53N/00127.45W'235/000/A=000239 !W31! id2047CF4B +000fpm gps5x3
it seems safesky are scrambling the real ICAO code when sending to the OGN - that seems like a very silly thing to do for compatibility