Also, I realized what bothered me about the 12mm front and 15mm rear setup and I don't think it was too much poke in the rear. I think the problem was there was too big of a difference between the front and rear wheels and that's what made it look odd to me.
15mm rear, 12mm front
From the factory, the rear track is already wider than the front by 35mm while the outside wheel edge sits the same amount away from the hub (total, so 17.4mm per size more poke in the rear than the front). Doing bigger spacers in the rear than the front makes that difference even more and it starts to look off.