Hi Robert,
Here is the response from Mr. Owens:
Yes plectrum strokes can be doubled as in MBC.
However in the example used the alignment should appear as below:
#G C–D-EL L EMDL- L EL-FM-
<B<B?? ? ? L ? ?N L ?? ??
,G ,C ,G
#AJ FLE-FMDL
? ? ? ?@C
,D ,G
If you look at examples 9.lj & k you’ll see an example of proper alignment. Example 9.11 has an error as the lines of the parallel should be shifted 1 space to the right.
Also notice that at the end of measure 10 there is a slide rather than a shift. Which slide you use depends on whether you’re sliding into another note, plucking or not plucking the 2nd note or sliding out of a note.
These are the sort of things we need to look at for further explanation so I welcome any questions and/or suggestions in order to make this as clear as possible.