The splines are about as wide as the clamping area on the prop so I'd say put it on until you can just see the edge of the splines. Clean the splines first, mine got some grease on making my prop fall off regularly.

Prop needs to go on front spline first, tap on until it will go on splines at rear, then tap all the way back until the pline area has disappeared, then a tiny tap forward and tighten.
Adam