Rectangular Baluster - Railing Panel not adapting to slope

[Andi]

Hi all, I attached a picture of my current railing. I'm trying to create a railing with panels between the regular round balusters. I was able to create this effectively on one stretch of railing by making a rectangular baluster family and adding it to the baluster layout. But any time the slope changes along the railing path (like at a landing), the panel doesn't adjust properly. I would like to avoid creating separate railings if possible, as that often causes problems with joins. Any ideas?

My ideal situation would be to create a panel that automatically adjusts to whatever space there is between the top and bottom rail and the balusters. It seems like that might not be possible.

Thanks in advance!