Oh what a trickster Walter is! I know you're probably not going to like this much, but is there any way you could test him at PM 6+? He seems to like to 'do his thang' at that hour of the night. If he's showing any sign of doing the swan dive, feed him some medium or high carb and head that boy off. I had a heck of a time initially trying to steer Luci with food. I know it's not great having to get up and down at night with these kids...if nothing else, put some medium carb into the auto feeder at 5 / 6 + to stave off these dives. I'd love to see Walter level off and stop with the moonshots...which are a result of the deep dives...I'm sure you would too.
Have a great day Zelda!