How much do nordica sparks pack out?

It doesn't matter. The 28 just has a slightly thicker footbed in it to take up additional volume, but that will pack too and end up fitting almost the same. I'd get either one and get custom footbeds done, as everyone can benefit from them, and they'll fit better.

well I wear a (fitting) 12.5 shoe size, and I use a 28.0/28.5 Solly(326 BSL boot).  You shouldn't be in a 28.0.  Get fitted, but there is no way you belong in a 28.0.  A tight fit is a good thing, you just need to get used to it.  Some places tell you to wear the boot for a day in your house a few days before ski season to get used to it.

  Have somebody that knows what they are doing check the shell fit since it sounds like you don't know.  Then, go get some good footbeds.  Some people like Superfeet..I like SOLE footbeds.  After those, get intuitions(you can order wraps and tongues, and return the one you don't think will work best).  Don't cheap out on boots, they are way more important than skis.

how are you in a 28? im a 10 shoe and ski in a 27 or 26 shell

some newb snowboarder at gene taylors fitted them for me. he got it off this foot measure thing that was made by nordica and it says for me (size 10) in a 28 boot.