Dual mass RS4 flywheel to one mass FW modification

[okkim]

Hi, I got a RS4 flywheel and resurfaced it. Then I got and idea to lighten it. I have opened the FW and removed the springs and stuff from inside. The original FW weights 12 kg, and now it is ~8 kg. I would still like to lighten it some more, but is it worth it? It could be done by removing material from the "back disk", and with that it could weight about 6-7 kg.

And then about these harmonic vibrations, are those so big issue that the whole project is worthless?

Here is some pictures what I have done:
http://www.valitalo.org/rs4_flywheel_machining.htm