draw package, multiple plots with different sizes?

Using draw, is it possible to do something like put one plot above the
other, with the upper plot being say a square and the lower plot being a
thin rectangle. To explain here is some sort of ascii art showing the
relative aspect ratios I want to achieve.

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All I see is the option to specify more than one plot, the number of
columns, and the overall size of the plot (the bounding box using
"dimensions"). I want to do this with the pdfcairo terminal.

Any suggestions, other than to make them separate plots and glue them
together by hand?