I'm not a C programmer, but it seems to me that you need to specify the clsf name to be used, such as CLSF_STANDARD. There is UF_CAM_opt_ask_clsf_names to get a list of the available CLS formats that can be used.
If you contact GTAC, the CAM team has a couple API experts who should be able to provide you with an example.
Is there a reason you are not using the newer.net API? I just recorded a journal and see that it is available: