I would just install the 105 brifters and see how it goes. As mentioned, there are different pull ratios between different calipers and generations of calipers that you might be able to find with some time-consuming searching. But, since you also have the 105 calipers, I would think it's just faster, and will give you a real-world answer, to just mount everything, try it out, and then switch calipers if necessary.