I'm building the same CG Chipmunk as you ricknkim. I've run into a spinner issue also.

The local LHS doesn't stock aluminum spinners but that's what I want on the plane. I'm using a Magnum 91RFS 4 stroker.

I ordered a Great Planes 2 1/4" spinner (my plans say 2 1/4 go figure). I also ordered the OS adapter kit for that spinner (they don't have a kit for Magnums but it's supposed to tbe the same as OS). Everything threads on just fine but the problem is that when I install the backplate, the APC 14x6 prop, the prop washer, and the first nut, there isn't any room left for the locking nut. The locking nut is also the attachment point for the spinner.

Am I missing something or do I need start grinding stuff down so it all stacks properly?

Mark