I finished my Pluto extension board this week. Further down you can find a link to some images in the german forum.
The add on board provides 40MHz fot the Pluto and 25 MHz for the LNB. Both derived from the same VCTCXO.
Furthermore it has an input for a 10MHz GPSDO to correct the conner winfield VCTCXO. I will put all documents on github soon:
Pluto Erweiterung 40MHz VCTCXO (0,28ppm) + 25MHz Ausgang + 10MHz GPSDO Ausgang