OK so I've installed the KBDFans rings on my Realforce too and this is what I've noticed.
As I've mentioned the KBDFans rings are stickier so you have to make sure you push the rings all the way down before reinstalling the slider otherwise it might stick then your keys might not come back up properly.
To be honest doing 104 keys was such a torture I'd probably not want to do this again.
So guys I'd say just pay the extra money and get the official one and save the time and headache.
But anyway here is what I noticed in terms of tactility:
Type Heaven (no silence) = Most Tactile, Most Wobbly
Realforce with KBDFans Rings = Less Tactile, Less Wobbly
Realforce with Hypersphere Rings = Least Tactile (though you can still feel a little bit), but very solid feeling (wobble is non-existent)So basically KBDFans rings sits somewhere in the middle.
Here is something else that I notice, Realforce somehow feels like there's more "room" compare to FC660C. Maybe due to keycap height so it give a false sense of travel difference.
So on Realforce even if I use Hypersphere rings the travel reduction didn't bug me that much, but on FC660C it
feels like it reduced travel so much I much prefer the un-dampened version.
From what I read NovaTouch and Topre RGB also give the sense of "more" travel so even when using silence rings people find it ok.
NovaTouch / Topre RGB = Most travel, so adding rings will not bug you as much, I don't own these but from what I read people even enjoy them with Hypersphere rings, and people actually recommend damping they think stock is too wobbly.
Realforce = Medium travel, adding rings might or might not bug people depending on how sensitive you are, KBDFans rings do reduce travel a tiny bit and dampen decently, Hypersphere I find it reduce tactility quite a bit BUT it completely eliminate wobble so it might be a fair trade off depending on what you like (makes the keyboard feel super premium).
FC660C = Least amount of travel, to be honest with this even KBDFans rings bugs me a little bit, with Hypersphere I find it kill the travel too much but again with the same argument as above since it completely eliminates wobble. I'd actually not recommend silent mod it.In any case, so mileage may vary depending on people to people.
At this point I'd say KBDFans ring is sort of jack of all trades master of none. It doesn't reduce travel much but also doesn't dampen as well. Hypersphere reduce travel a lot but completely eliminate wobble (feels premium). It's up to you to decide if it's worth the trade off.
Though I have yet to try the official Realforce Silent, but I suspect that will be the best of both worlds.
So at this point I'd recommend either leaving it stock or just buy official Silent (purple slider).