Hi,
What Eileen says is only valid for CPF coded packs.
From all PPF un-coded Packs, you can select any voice you want: Export as pack and import in a new pack.
The difference is that you won't be able to see the MSB position in the new pack except in the keyboard, as it is fixed by Yamaha.(Ex 48.002)
The advantage is that the MSB positions for users (ex.63.002) in the newly created pack remain empty, so you will be able to have more than 128 voices/pack.
Normally, the management of the original Yamaha voices, with a lock on the icon, should not overlap, but if it happens, you must give up one.
Regards!