This is both a bug and an improvement. The SoftLayer compute driver is using a lot of hard coded price ids. Some of them I believe have been invalidated some time between when the module was created in 2010 and now. Because of this, neither of the sizes works when I try to create new instances.
There's a new endpoint, which reduces the complexity of ordering a SoftLayer CCI.
This issue is aimed to fix this problem and serve as a general 'cleanup' task for the SoftLayer driver.