Hello Chris,
I plan to make exactly the same setup as you do, so I will be following your messages
Just for your reference: there is a way to 'stop' the xtal oscillator in the Pluto by grounding the enable/disable pin of the xtal. This way you don't need to remove it from the PCB and you don't risk damaging the board.
Credits to F4DAV for this modification.
73,
Lieven ON8HZ