UI RawImage over texture Quad bug

Hi guys,

I've got a strange problem when displaying a UI raw image ( a simple text ) on the screen :
Part (or all ) of my textured quads are not displayed depending on the depth of the raw ( rawimage is small and not above the quads ). Even if the raw image is outside the camera and the screen space.
_ if depth of the raw image > depth quad : everything's ok.
_ if depth of the raw image < depth quad ( raw image between camera and quads ) : some quads are disappearing depnding on the depth.
(I'm using UIDefault shader but that does not change with the standard shader)

 

Ok, I found a solution, I'd be glad to have your opinion about it :
I created 2 canvas objects :
_ One canvas with all "backgrounds" UI objects with layer = 0
_ Another canvas with all front UI objects with layer = -1