I wish to create a 12-30 9 speed Shimano cassette for road use. Sheldon Brown says this is easily done by taking a 12-27 cassette, removing the 14 cog & adding a 30 cog. My question is regarding the resulting shift quality from the 13 tooth cog. If the original 13 is designed for a one tooth jump to the 14 & now has a two tooth jump to a 15 with that not cause problems? Can that be salved by using a 13 from the xt cassette? Is it more complicated than that? Thanks!!