That sucks. If your cassette is normal (not a misfit), it definitely sounds like a hub geometry issue, to which the answer is going to be a spacer, unless you have a flawed hub. I'm not familiar with I9 hubs, so I don't know if they're designed to be run with spacers. Both of my mountain bikes have the better part of a centimeter between the XTR cassette studs and the leading spokes. Even if you are able to move the cassette out with spacers to clear the studs, it's unlikely that you'll be able to move it out far enough to clear the chain when it's in the largest cog and still have enough engagement for the lockring, again, unless that's how it was designed. Take pictures and post up. Picutres of both sides of the installed cassette will help. I'd also call I9 (828.210.5113) and get their input. They may want to see pictures as well.
Post up those pics and I (or somebody) may be able to help you out.
Good luck.
Post up those pics and I (or somebody) may be able to help you out.
Good luck.