Well here I am typing away on my FC660C after taking it apart and it is very enjoyable. Although I should state that I have actually taken this board apart once before already. The first time around was when I decided to dental band my board, and this time around, it was when I decided that I didn't want to type on ass. Pardon me, I know it's just opinion and everyone has their own tastes, but this is not how keyboards were meant to be used. Actually, no keyboard was ever designed to have dental bands inside of them, but that is besides the point.
For those who don't know what "dental banding" is, it's when you place a dental band, which is pretty much a smaller o-ring, over the stem of a topre switch and this ends up hitting the top of the housing on the upstroke dampening the sound. This ends up doing three things to be more exact. The first is of course that it dampens the upstroke making it much less audible and is cool because on no other switch could you practically dampen an upstroke. The second thing is that it makes the switch feel almost linear, yet not really. The very last thing is that the switch has a reduced actuation point. The last two points result from the fact that the switch is already slightly depressed from the dental band in between the stem and the housing.
If you want a straight up verdict out of 10, I shall deliver that up front for those who don't like reading walls of text.
Final Verdict: Edging/10
To be more specific, these domes have a sensation similar to what I imagine the act of edging to be like. I really don't want to explain what it actually is, but you can just look it up on Urban Dictionary if you need to. When you depress a dome on this, it sort of seems alright at first, but then the keys goes off. You know in your mind that it went off, but you really aren't sure about it. You've just put in all of this hard work just to get a sensation that is both disappointing and lacks all of the satisfaction of what you would normally get. Actually, it feels even worse to be more precise, more like edging while limp. You barely even feel anything on the downstroke. You can feel a little bit of something going on, but before you know it, you're done and you have gotten zero pleasure out of the experience and you question whether anything happened at all.
The one thing that differs between this and edging is that I would really suggest you find someone who has done this and likes it and use their equipment to have a go at it. It's just way too much effort for me to suggest to do yourself. Especially since you pretty much have to break the topre switches in order to do this mod.