What is the max number of shelves in a stack?
Can't find it in the document SAS Disk Shelves: Universal SAS and ACP Cabling Guide
Solved! See The Solution
It is a little cryptic, but you need to go to http://hwu.netapp.com/Controller/Index and select your version of ONTAP and the controller model. After you click the Show Results button there will be a link labelled "Compatible Shelves/Drives" which will contain all the information you need.
As a general rule it is 10 shelves per stack, but there are limitations when using the low end controllers and/or SSD.