Gnuradio for Raspberry PI 4 and SDRPLay works well, but need documentation

Hello all,

This email is a request for documentation on SDRPlay Source block in
Gnuradio companion.

I have been testing our Radio Astronomy Spectrometer and Event
detection with the SDRPlay RSP1A. It seems to be working pretty
well, using the downloaded OS for Pi from SDRPlay. They seem to have
put a pretty complete version of 3.7.13.4.

Swig and boost are installed and it was fairly easy to build the C++ code in
git clone http://www.github.com/WVURAIL/gr-radio_astro

I did update a few items, including VNC and SSH configuration, but
mostly it worked out of the box. I started with a Pi 3B+ but did
have some trouble running out of memory, so switched to a PI 4B (4 GB)
and the complied
code ran well.

Attached is a screen capture of the design, the inputs to the
SDRSource and the operating design. I seem many lines in the
frequency range 1416.5 to 1423.5 MHz and I'm wondering if I have the
wrong band pass filter selected. But I the SDRPlay source block
inputs don't well match the hardware layout (so far as I can figure
out). (The capture has the wrong frequency label, it should be GHz
not MHz).

I've goggled everywhere but have had no luck finding any document on
the sdrplay source block in gnuradio companion. Any suggestions?

Thanks
Glen