Visuals / config question

[Troy Yee]

Not sure where this question is most properly asked but hopefully 
someone on this list can point me in the right direction if this 
isn't the correct place. 

I am moving a legacy application to Linux with xorg server.  The legacy 
app uses an 8-bit PseudoColor overlay visual with transparency and an 
8-bit PseudoColor visual for image 'underlay'.  The Linux box has 
an nVidia Quadro FX 3400 card and is using the latest nVidia driver. 

When Overlay and CIOverlay are enabled, the server offers several 
24-bit TrueColor and DirectColor visuals that are not overlays and 
several 8-bit PseudoColor visuals as overlays. 

MaxCmapsOfScreen() reports 1.  The default visual is 24-bit TrueColor. 

Problem 1: 
I have no problem getting the overlay working.  I can't seem to get 
the 'underlay' working using the DirectColor visual (the application 
uses read/write color cells).  Even though I can create a colormap 
for the visual and allocate colors, the window is rendered using the 
colors from the default colormap.  I tried using XSetWMColormapWindows() 
but that didn't seem to have an effect (using KDE WM). 
 Q: Is there a way to configure the server to offer 8-bit PseudoColor 
    as a visual that is not an overlay (without giving up 24-bit 
    TrueColor/DirectColor)?  Even if I do this, will I still see 
    the same problem as I'm having with the 24-bit DirectColor 
    visual? 
 Q: What downside would I see if I set the DirectColor visual to be the 
    default?  I'm expecting to do some relatively high end OpenGL rendering
    on this machine after I get things ported.

Problem 2: 
In my first attempts I actually used a PseudoColor overlay visual with 
transparency for the overlay and a PseudoColor overlay visual without 
transparency for the 'underlay'.  When a window using the visual with 
transparency is stacked on top of a window using the visual without 
transparency, the transparent areas of the top window 'burn through' 
the window below it regardless of what colors are being used in 
the lower window.  I expected to see whatever was drawn in the lower 
window but I see the desktop (or a lower window that is not using 
an overlay visual). 
  Q: Is this expected behaviour?  If not, is it a driver problem or 
     is it related to the X-server? 

Any answers or pointers to answers are appreciated. 
Thanks, 

Troy.