Peter deserves all the credit for designing this great antenna. All I did was tell people about it. I believe a commercial version of the design is now available from VHF Teknik in Sweden.
Glad to hear you're using a preamp with the XDR-F1HD. Its adaptive noise reduction greatly reduces noise in stereo, but it doesn't function in mono and can't benefit mono DXing. The tuner does not have an RF amplifier stage so its noise figure is rather high (8.5 dB, about the same as a Technics ST-9030). Adding a low-noise preamp can really improve S/N for weak signals. As you note, the preamp gain covers up the soft-muting, which can be annoying at low signal levels. It also holds off the high-cut noise filter and this can improve intelligibility when trying to ID a weak station.