I honestly think there is more to it than custody. If that where the case then they could have just offed Hanna. Girls go missing all the time and disappearances are much harder to solve than murders. I would guess that money was a big motivating factor. I think George 3 saw that Chris SR was doing much better then himself. Plus i've heard through the local rumor mill that Rhoden SR had quite a bit of cash stashed back upwards of hundreds of thousands of dollars. Chris SR seemed like a very smart and frugal man. My grandpa always said that its better to be rich and act poor than be poor and act rich. I think the Rhodens were very wealthy. Even Chris Jr was rumored to flash thick wads of cash at school and around town.
I would be cautious about discussing rumors. I believe it is against TOS, JMO.