Ok guys! Here is another update!
I'm sure you have seen, above, that kenjack had a spare EXI CNC tail assembly and he offered it to me. kenjack made a brief video for me showing me what he had and it looked good to me. We agreed on a price and he shipped it to me even before I paid him for it. That's "trust"! The tail assembly arrived today and I have to say that the tail assembly seems to be even better than what I had seen on his video. He even sent me two pairs of tail blades. Awesome!!!
I did get the tail assembly mounted on my 500 and it definitely seems to be more solid than what I had with the stock parts. Unfortunately, it is late, so I'll have to wait until tomorrow to try it out. I'm really hoping this will solve the tail "hunting" issues. I really want to be able to fly this very expensive paper weight.
This part is for you, kenjack! Thank you very much for your offer and your speedy shipping. I really hope this works. About 10 minutes ago, I did send the money to your paypal account.