3750 supports maximum of 9 switches per stack. There is 3 meter stackwise cable maximum avialable in length.Check what will be the distance between the first and the last switch in your rack and then plan the stack accordingly. In gerenal practice, I have seen customer deploy a stack of 4-5 switches per stack.
If you have 12 switches can you have (2) stacks of 6 and then connect both stacks by fiber? Any disadvantages of doing this? At what point do you purchase a more robust solution (4510 or 6500 switch)?
You can create a stack of 6 switches and then uplink them using fiber. But why would you want to do that. The proper design would be uplinking the whole stack directly to the dtsribution/ core switches.
You go for 4500/6500 switches when you want a chassis based solution with more backplane throughput,scalability, PS redundancy, CPU redundnacy and other HA fatures.
HTH,Please rate if it does.
All we would have is 12 Cisco 3750 switches. I was saying to stack 6 switches and uplink this stack to another stack of 6 switches. Does this make sense?
Run them separately back to your core switches , I wouldn't tie them together , you would then be passing all your traffic up thru 1 switch to your core and have a major single point of failure.