[hpsdr] Penelope changes for Excalibur?

[n3evl]

I'm almost finished construction of Excalibur and will be ready to try 
it out soon.

I seem to recall some discussion relating to disabling the on-board 
10MHz osc on Penelope.

Have I remembered this correctly and is this considered an essential 
hardware change?

Is it only Penelope that is affected (I don't remember seeing any 
similar discussion for Mercury)?

I plan (initially) on using Excalibur's on board TXCO but will likely 
add an external ref later.

Can any of the Penelope/Excalibur resident experts clarify the need for 
this possible change and provide details (picture would be nice) of 
exactly what/where/how to achieve this.

Thanks, and Happy New Year to all on the HPSDR list.

Pete, N3EVL