I know EXACTLY what you mean! I'm the same now with Fred. I've switched him to Levenir, which has helped in the predictability of the pre-shots. Knock on wood, there are no more random low PS's that throw me for a dosing loop. BUT, he can have an incredibly high PS, and then go diving down. I didn't even know Levemir was capable of pulling down that much. Then, of course, we bounce. His nadir is also currently on the move. So I'll test him, and then be like, "OK! Should have one hour to go to ShopRite...go go go!".
My spreadsheet is a picture of what not to do, currently, as I've had to travel, and I reduce him for those times. So nothing has had the chance to really stick. I'm also completely paranoid.
I hope Wally is feeling better!!