After a couple of days tinkering I’ve arrived at what I feel is the optimum setup. The leg length depends on the height of the user, of course, and so is outside the scope of this review.
The SmartCRUTCH website mentions, as an aside, that some positions of the cuff are less stable than others (guys, you really need to give us full information on this – which positions are most, and least, stable), and in use I found the 90-degree cuff position provided little support.