Enforcing rows, but not column widths?

[bbimber]

Hello,

I'm trying to arrange 7 plots into two rows. I would ideally like row 1 plots to have non equal widths, such as 25%, 50%, 25%. On row 2, I have 4 plots and would like to give them unequal widths as well (such as 10%, 20%, 20%, 50%). There are no consistent vertical columns, and so the design formula approach does not work. Is there an approach to support this?

I looked at your examples for free(), which seems like a useful feature, but I did not see how to make that support this situation.

Thanks for any help.