I play with the McDermott I-3 shaft - that's 11.75mm tip diameter and the shaft has a European taper. I played with the I-2 with a 12.75mm tip diameter but prefer the I-3. The smaller tip gives me a sense of geometric precision where I strike the cue ball. As a side note, I went with the McDermott I-series shaft because of the no warp warranty as well as the shaft maintenance program. They'll clean the shaft, reseal it, and put a new Moori tip on it at no cost. The only charge is $21 for shipping and handling. I sent in both the I-2 and the I-3 at the same time and only paid the $21 for shipping and handling for both. That's a new Moori tip installed for 10 bucks. I've also played with an OB-2 for a couple of weeks and did not notice a difference in performance between the OB-2 and the I-3. The OB-2 ferrule was distracting to me. I haven't seen or played with the G-shaft but Scott Lee (a very knowledgeable instructor here on the forum) rates it very highly. Any chance of you borrowing a buddy's smaller tip cue before you buy one? Good luck with whatever tip size or shaft you go with.