It may not actually be at the far right, but it will be over there.
Open and read the template. It is the documentation as is the web page.
Graham, the actual placement will be determined according to the names of any loaded Add-Ins that modify the QAT along the lines spelled out in
Modifying the QAT and Ribbon in Microsoft Word. See "Order of Icons."
Since your Add-In starts with "S" its icons will be near the end if not at the end.
I tend to have a lot of small Add-Ins running some of which add to the QAT. I would guess this is true of very few users. In my case, my old WordArt gallery ends up behind yours.