Hi Ian, welcome!
Bond API doesn’t support any way of encoding the body of the request into the URL. I guess you’d expect something like PUT http://IP/v2/devices/1234567812345678/actions/SetSpeed?argument=3 ? That’s something we do not support. However, just about any HTTP library should allow bodies in the requests… that’s standard REST API design.
Maybe take a look at @SDamiano 's work? OpenHAB Integration