All right my fellow freaks..

[pete236]

Figure this one out:

I converted my mCX2 to the S300 with all E-flite parts which included the lower white blades.

Took off on the maiden and it vibrated so badly control was an illusion.

I slowly (part by part, blade first) reverted back to the mCX2, with no resolution.

Once complete, all vibration vanished!

I pretty sure I'll keep the mCX2 intact and buy a mCX to convert.

[j369fox]

I'm not sure if this will help you...

When I first put my carbon fiber tail on my MCX2 it couldn't even fly because of the vibrating tail. I tried all sorts of goofy things i found online and nothing seemed to work. Just this morning I took to bottom gear off and put it back on and it is 99% gone and flies very well now. The last 1% percent i believe is due to the fact that the gear isn't tracking perfectly straight now.

You could try just loosening up the mounting screws. Then and pressing down on the top rotor head and the bottom gear to seat them all the way together and retighten the screws. Hope this helps because it worked for me today

[pete236]

Nope, I tried that.

[Pfloyd]

mcx2 frame is slightly different than the mcx frame.
Also, the tail boom for the s300 is shorter than the stock mcx tail boom.