Hi Jeff,
I'm by no means a Luftwaffe expert, but I've never seen the 2cm Pzgr40 used in any other case than the S18-1000 long Solothurn (20x138 B) , and my understanding is that the Luftwaffe tended to use the cannons such as the MG151 as compared to the S18-1000 they were lighter, had higher rate of fire and far less prone to jamming which would be critical factors for air to ground. The 10x Pzgr40's Steve found I can only assume were from a 10 round magazine for the Kwk30/38 which I believe only used 5,10 & 20 round mags, due to jamming issues.
Ill do some more research but to my knowledge they were only used in the Heer, Panzer II (Kwk30 & Kwk38) and Sd.Kfz 234, 222 etc, armoured cars. Whether or not magazines were supplied to Flak38 (FlakPanzer Ostwind, Wirblewind etc) units for AT usage I also don't know.
If anyone has more specific info on usage, please post.
Rich