Follow #2: on my second Klaxon device - Klaxon Mini - I replaced the display with the EggRider v2 Bafang version and this worked to derestrict it. Before it was restricted to 10mph, it now revs to 17mph.
Note, my first attempt I replaced the display like-for-like did not work as on the DP C15.UART display you cannot edit the speed or wheel size settings. So I tried the EggRider and it work great!