Loose Steering Wheel

I currently have a quick release steering wheel (tratter came like that) but when fitted it seems a have a fair bit of play between the splines and the boss.

The shaft isn't 36 or 48 spline, its got a large "flat" spot on the shaft to key the steering wheel.

Any one else experienced a loose fit with quick release steering wheel bosses?
Any idea how i convert it back to say a 48 splined interface so I can go for a better fitting quick release system?

Replace the shaft, it has obviously been doctored to suit the cheap quickfit.