That's interesting, KR. If you had handed your sponsor a letter of resignation from the SGI, then from that *moment*, their rules could not be applied to you. If he went ahead and tried to confiscate your gohonzon (and you could document it) and the organization had excommunicated you officially, you could have taken them to court and won some tens of thousands of dollars in damages, maybe more:
It is your legal right to resign from *ANY* religious organization for *ANY* reason at *ANY* time. You have the right to resign unilaterally, completely at your discretion, and the religious organization may not put any conditions AT ALL on your leaving. None. They can't require you to return your gohonzon. They can't point to that contract you signed when you got it and say that because it says you have to return it, that means you have to return it. At the moment you resign, their rules and bylaws cease to have *ANY* hold on you. You are no longer obligated from a legal standpoint to "play ball," much as they would like to order you to jump through hoops. Throw your gohonzon away - that's what the SGI is going to do with it anyhow, you know. You DO realize that, right?? It's worthless - the only way they were able to get money out of you for it was to manipulate you into BELIEVING that it was worth something. It's just a piece of paper and some crap wood dowels (or plastic!) with a little scrap of yarn. Take out the trash.
For anyone who is interested, this is a site providing instructions on how to officially resign from the Mormon church, but just change "LDS" and "Mormon" to "SGI." They have several templates you can use as a jumping-off point - just personalize them as you wish:
Remember, unless you officially resign, the SGI will continue to claim you as a member, pass your personal information around, and use YOU to inflate their membership numbers in order to claim more power and influence than they really have. Granted, you have no way of confirming they actually did as required, but if you catch them passing around your info, you can sue the pants off them. And I hope you will.