what is the max length of a command that can be issued to the ssc32?
There is no theoretical limit to the number of bytes in the command. The incoming bytes are buffered in a 128-byte queue, but the firmware checks and empties the queue frequently, and can keep up with commands of any length at any supported Baud rate. The longest command I would expect anybody to send is a group move with pulse width and speed for all 32 servos at once, which would be around 450 bytes (more if spaces are used to separate parts of the command).
There is, however, a limit that must be observed: a group move command may not specify pulse widths for more than 32 servos at once. That may seem obvious since it’s only a 32-channel controller (which is the reason it’s not mentioned in the documentation), but I’m stating it here for completeness. If you were to send a long group move command, and repeat the pulse width for some servos, some versions of the firmware would not like it, and would ignore all pulse widths beyond the 32nd.