Turbo back in!!!
I installed these calipers + Sonata rotors yesterday and I concur that the GT alloys DID NOT fit. All were brand new parts (except for calipers) and the pistons hadn't been compressed yet. I had to go and get some wheel spacers (only able to grab 8mm ones) and put them on to get proper clearance. With those spacers, I had only 4mm clearance between the caliper and the ''branches'' of the GT alloys. (I will go back out later and measure the clearance once the piston has been compressed, I doubt there will be much difference).I posted real quick on my way out the door at work. I was thinking about this and I realized that the steel wheels are the ones that fit and the GT alloys did not.
Here is what I think is going on. When I did a test fit the brake pads were brand new (full thickness) and had also not been put under pressure by the piston yet. Because of these things the GT alloys did NOT fit over the Tib calipers.
I think that when Evan938 tried the GT alloys he had some wear on the pads and they had been compressed to some extent by actual usage. Thus allowing 2mm clearance.
So worst case scenario is that a brand new set of pads on Tib calipers may not fit until they are worn down slightly. You may be able to sand a millimeter off each pad as well but I don't recommend this.
However, I must say that this setup brakes really well. I love how the brake pedal feels now compared to when I had the Elantra calipers.