Well I've been using the xpen configuration suggested by Markus and it's the best setup I've used yet, they really seem to like it! This was the one they were in when they got into the litter pan together.
But yes, I think the confined spaces of the single pen seem to be too much for them. (I did combine the top of one superpet pen with the top and bottom of the other, as I posted in another thread) I think I may have to just stick with the separate night pens, since I simply can't stay up all night for who knows how long to make sure they don't fight.
Pip is in a real snit today and has been throwing her litter box all day and most of last night. She only does this when she's extremely unsettled. Everything was fine until I tried to put them in the same bunk bed.
It'll easily take me awhile to get her calmed back down. And until then, she's just too dangerous to be around Mimzy without someone sitting right there to keep her from taking it out on him.
Their routine has been disturbed and now I'll have to work hard to get it re-established.
The nice thing is, the next Binky Box arrived and they got to try those new dried willow bundles with the leaves still on? OMG, did they snarf those like their butts were on fire! They LOVE them!
So that made us all quite happy today. ^_^