Do we have an idea which data center supports the largest virtual machine size? We understand that the largest public virtual instance can go up to 56 CPU cores and 242GB memory, but not all data centers support that. However, in SoftLayer autoscale console, we can see this instance can be selected in all the data centers, but when you create the autoscale group, you will fail for some data centers saying this size is not available.
I suggest you to submit an ticket to softlayer and ask them that to the Softlayer's sales guys.