<<< Hello, Gary -
Nice looking FSL, and well-demonstrated.
How would you expect the performance of the setup in the video to compare with the performance of a Sangean PR-D15?
Since I don't have a Sangean PR-D15 it's tough to answer your question, but I do have multiple Sony ICF-S5W models, which are regarded as some of the most sensitive AM-DXing portables ever manufactured.
The CC Skywave + 3" Baby FSL combo will clearly outperform the ICF-S5W stand-alone portable on all frequencies from 530-1700 kHz, although you do need to peak the Baby FSL's tuning cap whenever you chance the frequency, so that does add one additional step in the DXing process. As for the reception of the 1070-CFAX daytime DX signal in the Baby FSL demonstration video, the Sony portable can receive it at about an S7 level, whereas the stock CC Skywave only manages about S2, and the Skywave-FSL combo manages S9++.