Part of me wants to raise an objection, but then that would just make me look like the bad guy in denying S4 to stay an extra night with his mother. And in a way she is doing us a favor in watching S4 while I am with S8 in his Monday night cub scout meetings -- I just wish she would quit taking advantage of that to convince S4 to spend the entire night with her instead of just the evening.
To make matters worse, she forgot to pack the very same bedtime stuffed toy with S4 when returning him today. Fortunately S4 didn't seem to notice and managed to drift off to sleep tonight bereft of such comforts -- which just underscores my suspicion that xW instigated the whole tantrum S4 threw last evening over this toy.
I am now inclined to deny any further requests by S4 to stay with xW during my weeks of custody, except under special circumstances. Even if it makes me look like the bad guy.