can dest-pane colwidths be set from the source-pane ?
thx 
Is the aim just to get the same column widths everywhere, all the time? Or do you need a way to do ad-hoc resizing and then apply the same size to both sides, where it might change each time?
Thx Leo, the latter.
It should be possible via a script which loops through the columns on one side and sets the widths on the other.
I was hoping to try writing it myself but haven't had time, and probably won't for a while. But if you want to have a go, this script might be a good starting point as it changes column sizes in the active file display. Not exactly the same thing, but related.