yeah you would have to use the bearings meant for the 6mm shaft but you should check to see if you can re-use your original bearings, maybe just swap out the ones in the blade grips.
as far as the upgraded Feathering Shafts. Microheli kinda screwed everyone on that, especially me. They promised to make them, I sent them my parts ($75 for shipping) and I haven't heard a response from them in almost 2 months, they never made the upgrades, they never returned my original parts and they never refunded the money I spent on shipping them the parts.
So feel free to send them some hate mail
I was trying to help them make money and promote their products, The ONLY thing I ever asked in return was that they make the Upgraded Parts that people (myself included) wanted to buy, also parts that weren't for sale anywhere in the world. Trying to help them make money and I got screwed.