Add-on scenery in flight plans

I have added a lot of Australian scenery to the 'addon scenery' folder and it all seems to work ok. My problem is that I can't seem to find a way of creating a flight plan from a 'built-in' scenery airport to an 'addon secenery' airport. If I set the start point from a 'built-in', then the ddialog box for "search add-on scenery area" is greyed out, and vice -versa. Can this be done?

the add on scenery needs to be in the master database. I believe you need to place it above the default scenery in the stack. if it isnt above the default then i dont think its data is read into the master database. at least thats what i am getting from several of the installs i have done so far.