resolution issue in a windows xp vm inside a retina macbook

I have a macbook 15 with Retina display and I run a windows xp virtual machine inside Fusion.

I enabled retina display support.

The issue is that even if I set, in windows, the desired screen resolution (1680x1050), it keeps getting back to 2880x1800 (which is unusable) every time I restart or even just unsuspend the virtual machine.

Is there a way to fix that? Or some workaround (a batch to click and set manually the screen res. every time is needed)?

Thank you.

PS Fusion is 5, updated, and also XP is updated with latest patches and so on. I am using it as an administrator user.