After some internal discussion I was reminded we still support some Query String GET requests to our SSP. I'll have to dig into numbers, but I'm fairly sure this won't work as currently designed, as the blob has to be passed in the body of the request using JS, which basically means using POST or PUT (docs seem to confirm this).

Can there be an option for the browser to include this in a header? If the link is coming from some HTML element we could have some attribute to tell the browser to include it...I guess if it's being sent by JS (but still needs to stay GET based for whatever reason) we could just make our own X-blob header, but if there is a way to support it with some canonical X-PS-blob in all cases that would be good.