[ncl-talk] Problem with panel plot

[Appo derbetini]

Dear,

I am trying to do a panel plot which contains:

First line: mean precipitation (observations, models)
Second line: differences between observations and models.

In the second line i want to add t-test.
But theses errors appear

fatal:NhlAddOverlay: plot class mapPlotClass cannot be overlay plot member
fatal:NhlAddOverlay: plot class mapPlotClass cannot be overlay plot member

Someone can help me to solve this issue?

Attached script I am using and the plot I am having
regards.
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