Trimming and mounting Van's spinners

[Wicked Stick]

I would appreciate anyone's experience on the best/easiest tips and tricks/procedures they've found to get good results on trimming and installing a Van's 12" spinner kit onto/around a Catto 2 blade prop.

Van's spinner kit has just arrived, and right out of the box, the edges of the spinner seem to be uneven when I place it on a flat table. I knew I would have to trim the cut-outs for the blades, but I didn't expect to have to square up the back end too .