Raster Manager

I hope someone can help me out. I want to set my aerial image to background in a dwg and save it in that setting. 

So to explain, in a dgn I attach an aerial image in raster manager, under properties, display print, plane, the setting is background. So all my line drawings sit on top of the aerial image.

In a dwg I attach an aerial image in raster manager, under properties, display print, plane, the setting is design. I can change this to background but it wont save in background and every time microstation auto saves it goes back to design and my line drawings are now in the background. 

I'm attaching the same aerial image from the same folder into the dgn and dwg. 

I would like to have the default in dwg to background. Can anyone help?