its a good idea if your still growing because the boot will fit more snug in the beginning of the winter and eventually pack out ore and more, therefore, adjusting to you as you grow. It will fit almost perfectly.
Not to mention that this is an awesome boot, i would def. go for it in 28's
yeah id say definatly dont go into a 28... see a boot fitter or just go and try them on yourself and see how they fit, try a shell fit and make sure your heel doesnt lift up when your in the boot. never buy a boot with out trying it on. You will be very dissapointed if it packs out and its to big for you. if your thinking about "stepping up a size" i wouldnt. You can always make a boot bigger by grinding the shell out or packing it out but you cant make a boot thats to big for you smaller. just trust me