I did a quick calculation checking your skew-angle (some figures were hard to read in the drawings, very small print), but I think your rotor length is 105 mm, the magnets are 20 mm dia and the outside diameter of the rotor is 87.5 mm. If this is correct then your skew angle should be 4.37 deg (see this image for the calculation: http://www.anotherpower.com/gallery/decogging/figure_27) I am using a slightly different variant of Zubbly's rule which should yield less cog. But I expect that the 'simple' rule of skew by one slot will work pretty well too, as you have 5 magnets per row, not 2 or 3 (in which case you NEED to make a correction). However, as it's just as much effort to skew by 4.37 deg. as by 5 deg, why not do it the proper way ?

Only worry I have is that part of the magnets will be outside of the stator and that this may interfere with the decogging. I.e. it may cog a little bit because of this.

I doubt it's really much of an issue in practice though. A very slight cog won't hamper performance much.

Looking forward to the rest of your project,