Bad Shed.

[Vengeance]

My Cali King just went through its first shed with me and it didn't go so well. It didn't come off in one piece, he was shedding last night so when I get home from work today I'll see if he retained any. If there is some shed retained I'll stick him in a Rubbermaid with a damp towel for a night to clean him off, but what am I missing in terms of husbandry so that his next shed will turn out fine.

He is in a 20 gallon glass tank with screen lid
Substrate is carefresh
Has a cool side of 76o F
Hot side of 90o F
2 hides, one on each side + he borrows everywhere
Water dish large enough to soak in

I know glass tanks and wire lids are not good for humidity but I was under the impression that Cali kings were a low humidity species. I haven't been keeping track of the humidity in the cage for that reason. Any suggestions on how to make sure he sheds fine next time around?