Graham, I have just run into some issues with my 600 and I have a feeling that I"m going to be right in the same boat as you are. If you have read the posts about the heli, you know that no matter what I do, something is always wrong with this heli. There is something hinky with teh head, and I can't find the cause. For this reason, I'm thinking about putting the thing on hold until I have the $150 for the complete DFC head and swash upgrade. However, when I do this, I will have to change the one way bearing as well as the lower bearing support to the one with the smaller diameter as you are having to do. Hell, I'm thinking about scraping the entire heli kit, ordering a new kit, and starting over with something that I know is going to work, adn work correctly. Not this "thing" that some guy that didn't know what the hell he was doing tossed together, couldn't figure it out and sold it cheap. Yeah, nothing is ever cheap, there is always a reason lol.