Today's grabbing results were OK-ish. Not really good, however, the additional r.f.-stage helped, however, the shift the filter frequency prevented the break through.
The 22pF I experimentally confirmed for the version w/o the additional stage are now shifting the filter response far more upwards than wanted. To be more flexible, I decided to replace the 22pF capacitor by a trimmer capacitor with a maximum capacitance of 18pF. The first results are promising. The filter response is now centered to 10140050Hz, which hopefully provides much better reception than I gained with the last design....
Wish me luck!