Vbox - v 5.0.10 r104061
I'm using a notebook with external monitor for the guest, the native resolution is 1920x1080x32 but the full screen resolution is getting 2400x1350x32, worse the 1080 resolution is not listed and when I forced, had just a small screen in the middle of a 23" monitor.
ps: Scaling does not fit in any way.