Having a problem installing a new steering wheel

[KMACD71]

I'm putting a new steering wheel on, and am curious as to how much the shaft should move in and out.Mine moves about a half inch.I need that half inch to get the nut back on and enough of the new adapter to seat in the splined shaft.If this movement is normal,how do I keep the shaft from moving back down when I put the plastic canceling cam and adapter on the shaft?Any advice would be appreciated.Thanks.