So for anyone else reading this, after MKSA’s extraordinarily helpful comments, I’ve been experimenting with various alternatives to this coupler.
I’ve tried universal joints, both printed and machined (I.e. purchased) and also flexible couplings. I’ve also tried the original rubber tube supplied with the CTC i3 Prusa Pro B. All of these produced inferior prints to my coupling design, some really bad (flexible couplings were awful).
Obviously this only applies to the CTC i3 and I can only speak about my experience, but if I were you I’d use your own judgement rather than listening to piffle from self-proclaimed experts.