Is it possible to use the concepts of containerization and embedded blobs with XAM?

I understand that embedded data can be configured globally by setting the FP_OPTION_EMBEDDED_DATA_THRESHOLD value, and I assume that this will also be applied when using XAM to ensure that the XStream is stored in the CDF?

To implement containerization, is it simply a matter of managing the metadata (i.e. indexing into a byte array of all files to be "containered") as fields on the XSet?

Regarding the FP_OPTION_EMBEDDED_DATA_THRESHOLD, I have read that the normally recommended maximum is 100K, however this can be increased to 1MB if necessary. Is the appropriate choice here based on the difference in time to base64 encode/decode the blob, compared to the time taken to perform two writes/reads? (i.e. CDF and blob)

I will more often than not be dealing with blobs of an average size of ~300-400k - why wouldn't I store these as embedded data?