Screen resolution switch with DGA

[Sherwood]

This has me baffled. I run Diablo 2 under Wine, works absolutely 
flawlessly in every way. I have DGA enabled, and a 800x600 desktop (also 
tried the Managed and Unmanaged options). Thing is, my X desktop is 
1600x1200x16bpp and of course Diablo 2 is only 800x600. Is there any way 
to have this resolution automagically change to 800x600 (nothing seems 
to do that here), and back when I exit it?

I know it's not a problem with my X. Countless other games support it 
[SoF, Wolfenstein,... ] under X.

Running Codeweavers Wine and XFree86 4.1.0

Help appreciated...