OK, so I DID IT, I modded my Leopold FC660C 2014. Lubbed the stabs, modded all the keys. I thought some remarks from a noob could help. A lot of obvious stuff but when you're a noob...
I ironed the landing pads to death (it took HOURS - well, a bit more than 2), ironed 160 because I plan to do my RF 87U too. Pro tips: a wood cutting board is nice to do this UNLESS they are in 3 glued parts. At the end you will have 3 small cutting boards when you'll wash them... :x )(been there, done that).
You WANT to iron those landing pads because the travel of the key is REALLY killed by the normal sized pads. No they can't really be "too thin". And I didn't burn one even at max temp.
Opening the case is not that hard (1st screw is under the small OK sticker, not the BIG middle sticker...)
The work is TEDIOUS but worth it, really. I think I messed up only 2 keys and the spacebar. 2 keys produces some "sticky" sound, dunno why yet. The space bar is totally silenced (lub ftw...
) but the travel is too short, maybe because of the landing pads I used on the stabs (the switch use the same ironed landing pad). I'll check that later, right now I have some work and doing it on this beast anyway.
Don't check out the sound of the switchs on the plate only. The sound is totally different and much better when you'll put back the PCB & plate together. They need to be sandwiched by all those screws. Don't panic if one modded switch is a bit lazy and don't want to go down by itself easily. I had 3/4 like that and it's not a problem. A REAL trouble would be a switch staying down, but I don't even know if that can happen with this mod.
TL;DR : this mod takes HOURS, totally worth it and if you're lazy you can only do it on mods I guess. On my FC660C 2014 they were horribly noisy and now it's a dream, HHKB-Type-S-Like-only-better. I used stab wire lub too btw, it helps a lot, especially on the spacebar.
Thanks again SpicyBar for the idea / research and post!!!