Hi Peter,
First, a correction to my message above. I was wrong when I said “Spotter does not add anything.” It adds a 29-byte header with location and diagnostic info, so the max user payload is 311 bytes. See More info on "growing set of abstract parsing tools" - #8 by zachary
And then to answer your question, no, there is no way to directly access the cellular connection. The closest you can come from a dev kit is by using spotter_tx_data.