Thanks, greenja --
I took a closer look at the Data Throughput example, and found I could work around my problem by using a burst of 20-byte packets.
The Data Throughput example uses bursts of 3 x 20 -- Are you aware of any reason not to do more at a time? My biggest current logical packet takes 87 bytes, and I seem to have no trouble sending this data in a single bust of 5 notifications.
Also, at some point I came across a 23-byte buffer declaration deep in the bowels of the code, where it was pretty clearly a direct limitation on outgoing payload. I wonder if this is just byte-miserliness, or if something else breaks if you make this bigger?
Does anybody know?
Thanks again