Well, getting OT here but on my board it was very loud with regular typing. I'm happy that your linear red board didn't have the same problem, but please don't assume it was a minor issue on my board merely because it wasn't loud on yours. I wouldn't have taken the foam step if it were minor. It still might be insane using insulation foam on a keyboard, which I readily admit, however it was loud and annoying enough that something needed to be done. Mousepads and other attempts at sound dampening were ineffectual. I could have RMA'd it, but decided to try to fix the issue instead, and luckily I was able to reduce the ring.
It's your board to do what you may with it, so no problems there. I'm going to have to refute the claims of this pinging sound actually being a problem, however.
The right side of my board sounds JUST like yours does in the video. Hitting everything from the ] key and right sounds exactly the same. It's almost definitely something to do with the vibration of the mounting plate as the pitch gets higher and eventually the 'ping' goes away entirely once you get to the G key or so. Typing normally, though, I really have to strain to hear this 'ping' sound on anything except when I'm smashing the Backspace key.
Reds are 95% the same as browns, absolutely wont make a different if it was the springs vibrating. If anything, the small bump in browns would reduce the reverberation on the rebound. I have decently sensitive ears and find this noise not more than the tiniest of nitpicks and, if anything, add a little character to the board.
I realize that you probably have HYPER sensitive ears (or you're typing like a jackhammer) and it bothered you enough to bring your keyboard to hell and back but I really think this isn't the board and just something mostly in your head and there's a bit of FUD going on amplifying the concerns about it. When I think about someone buying a SteelSeries or a Meka or a Razer instead of a Filco because of "key wear" or "pinging" concerns I get very sad.