Sensible Burnup Chart with Cumulative series?

Hi, folks,

I'm trying to put together a burn-up chart, and there are some things that are really bugging me.  I'm not sure if there's a tick I don't know or if what I want isn't supported.

What I want to do is draw a burn-up chart for my release, which is expected to be N iterations long.  I'm plotting the number of story points Analysis Complete, Development Complete, etc., by creating a plot with cumulative series based on hidden fields for "Iteration Analysis Complete," "Iteration Development Complete," etc.,

My problem is that I can't find a sensible way to model the fact that we're part-way through the release.  What I ideally want is for ONE of the lines (the scope line) to run all the way across to the end of the release (so we see what the "target" we're aming for is), but I want the "data" lines to stop at the current iteration.  I can't figure out how to make this happen.  See example below--I want the black line to run to iteration 31, but I want the red, blue, green lines to stop at iteration 25, not run horizontally. 

I could partially work around this by using x-labels-end (as JoeZ found in his post below), but that's not really what I want, because that will also cut off the total scope "target" line.  I'd like to eventually add some "target" lines to validate that we are/aren't on pace to finish on time, so I don't want the whole chart to end "now," just the data lines.

What I'd really like is some way to set some equivalent to x-labels-end ("stop drawing after this point") on individual series.  An alternative would be having a series-level concept analogous to trend-ignore: zeroes-at-end (i.e. stop padding forward with zeroes), but that seems to only be an option for trend lines, not "real" data lines.

Any ideas?