EA cases are tricky things and I really wouldn't recommend using them for anything other than EA. The problem with them is there are so many different variations of the case thickness it's really hard to make inserts for them. There are the super thick EA cases, then ones that are just slightly ticker than a standard Sega case and even ones that are a little thinner, plus I don't even know how many in between. If you want to store S&K in a clamshell, I'd strongly suggest doing this:
Just cut out those 2 small pieces from a regular clamshell. The plastic is surprisingly easy to cut with a sharp knife or razor blade. The S&K cart fits just fine into a regular clamshell, even with the manual, it's a snug fit, but it works. Plus this way you can have it in a case that has a hangtab and will it fit right in next to the other Sonic games.
And yeah, if you want to send me the scan I'll give it a shot. Just please scan it at at least 300dpi, though 600 would be even better if your scanner can manage it.