John,
I have never tried this, it seems like it should work, but is there a subtlety waiting to bite me?:
due to spectrometer configuration issues we have the following 3-passes setup for mapping on a 4 spectrometer probe (nominally using MAN background):
Round 1
F,O,Ti,V
Round 2
non,non,Cr,Mn
Round 3
non,non,Fe,Co
So the question is:
If I wanted to use off-peak backgrounds for F and O, could I collect the HI and LO bkgd using a non-conventional method in rounds 2 and 3? e.g. in PI, for round 2, set the PI 'on-peak' position on the unused spectrometer to what is in reality the Hi bkgd position of F (or O); likewise, in round 3 set PI 'on-peak' to Lo bkgd position. Later, in CI, I would define the round 2 F and O maps as the HI bkgd and round 3 F and O as the LO bkgd.
Granted there may have to be some manual file-renaming at some point, but do you think this would work?