I may be out of order here, but in my experience, there is no need to add anything to the spamassassin package selected by the Devs for the SME server. I have a number of Japanese users, and stock SME appears to be doing the job nicely, this being especially true for Version 7.2 just released. For example, on a server receiving over 2000 spams a day at the front end, under 7.1.3, I used to get say 20-50 stay spams for all of my users a day, asnd another 5-10 false positive (yahoo mostly...) Having upgraded to 7.2 over the past 48 hours ago, I note that this had been reduced to around 5-10 stray spams per day. Very very nifty.
I suggest you upgrade to 7.2 and remove any additions to SA, - and see.
Then worry about customisation if required and justified.