no, ok.
I meant you shouldn't go in 1280 , with dgvoodoo, cause it's campionated at 1024x768, that should be the highest resolution to play with those panels/settings .
firstly mind to keep mirror details without the "as forward view". Keep it to "None", since that eats so much in PO required.
but if you use dgvoodoo exporting (is the better solution) , and leave in 512 (it's already oversampled in 1024x768 ) and check how is going if it's playble (PO).
if you want put it at 1024x768 (but mirrors still to "None"

and check again, but anyway notthing over 1024x768 has sense.
You may also go in the
"C:\GP3\Utility\dgVoodoo" and dgVoodooSetup check the settings for the folder c:\GP3 and check to disable apply phong option or linear filter or nomipmap activating. I suppose it may give a bit more performance.