Because the sound goes hand in hand with the fit my friend; where one is flawed, so too is the other. I honestly don't think a re-fit would take nearly as long as the original shell. If anything, at most, I could see Adam comparing directly to your original impressions (which of course he sent with the reshells), and seeing where the dimensions differ by even the slightest on the reshell, only requiring but a bit of extra coating here or there. I'm no expert on the matter of course, but that's just merely my take. Believe it or not, a few here have also suggested and had luck with applyig a coat of nail polish to the outer shell, in whichever areas they felt the shell needed but a tad bit more coating. Not to mention, the JH16 pair I originally purchased had dried up nail polish on the outside for this very reason (which the second owner informed me of, of course), and all it took was but a gentle wipe of nail polish and I was able to remove the entire extra coating of nail polish it with ease. It's a simply DIY, assuming that one is careful not to get any polish around any of the bores, or anywhere too close for that matter.
Nevertheless, my recommendation is to take advantage of the re-fit that's offered to you for this very reason. It's quit honestly one of the main reasons I went with Kozee. Bare in mind however, you do have a 90 day refit guarantee, which gives you ample time to decide, and based upon the feedback, more often than not, the second time around is the one that ends up just right, with just about any refit (be it via third party or the original manufacturer). But if the sound is as "perfect" to your ears as you find it to be, then the fit may very well be good enough to not worry have to worry about it in the first place.