Good to know that the rings seem to be working out well on a variety of Topre-switch keyboards.
Regarding opening cases, by far the easiest ones are the HHKB Pro 2 and the RF87U. In contrast, it seems that CM doesn't want people to open the case on a Novatouch. This makes me appreciate the HHKB and RF boards all the more -- no hidden screws, no seals to break, no violation of warranty just by opening the case.
Just remember -- on the RF87U, don't install a silencing ring on the Left Ctrl (far left key on the bottom row). This switch is designed differently from any other on the board. A silencing ring won't work properly on just this one key; furthermore, it will cause the key to jam.