Enough people requested an answer to warrant a public posting.
If you have two spectra that you would like to compare with the same
resolution in XWinPlot there are two solutions.
1.) Use two 1-D plots. You will undoubtedly need to type your limits
and positioning variables in manual under the edit pop-up window. I
didn't try this, but about 50% (of 6) of the answers were this.
2.) Use the DC variable in XWinNMR to alter the height of the "faulty"
spectrum. First use the dual display in XWinNMR to figure out how much
the spectrum needs to be scaled. Set DC to that value and use the mulc
command. Then when you update the data in XWinPlot the spectra on the
stacked plot will be scaled appropriately. This method worked well for
our purposes. One caveat: it wasn't overly obvious (until after I
figured it out) that if you scale your spectrum by .3 and you realize it
should have been .35, setting DC to .35 and using mulc again will scale
an additional .35, not .35 of the original spectrum. If you want to
scale from the original spectrum, re-FT, which removes all scaling.
As an aside, there are mixed feelings about XWinPlot, most of which
are also voiced in my department as well: the main being "it takes to
long to learn." Apparently people want a one-click solution. Use of
autoplot and setting the reset options accordingly in XWinPlot did *NOT*
set the limits as I would have hoped. Perhaps I am doing something else
wrong. In any case the other complaint, that of poor resolution due to
the width of the line used to draw a spectrum, can be solved by setting
the line attribute to super-thin, which is identical to XWinNMRs
line-drawing width. Perhaps this should be the default setting for a
future version of XWinPlot...
Thanks for everyone's input and I apologize for taking up so much
bandwidth.
BoB