Questions for @xzcc:
Have you tried the Rockchip CWM recovery images at androtab.info or were you rolling your own?
Do you have a method to unbrick DX50 if the recovery flash procedure fails?
I've tried an image from androtab.info for our processor. Never tried to dig into that stuff with customizing recoveries.
Of course every time I tried I got a brick, and unbricking is absolutely easy with Rockchip Batch Tool.