XML draw-erase options?

I've got a bit of experience with most aspects of design for FS, but gauges are still a "black art" for me... so please forgive the ignorance demonstrated below ;)

I am trying to replace a HUD gauge in an aircraft in FS9. The original gauge is written in C++ and makes use of the "no_static_blending" flag. Also, I'm fairly sure the aircraft designer has made the material for the HUD poly slightly opaque.

When I replace the original C++ gauge with any of the XML HUD gauges out there the gauge draws correctly, but does not erase/update the previous frames. So you can imagine it becomes a big, green mess when the gauge is drawn 30 times per second and none of the "old" draws are erased.

I guess this is because xml does not have the "no_static_blending" equivalent. Is that correct? If yes, is there an option in xml to explicitly erase previous frames? I've seen the "image_erase_always" development for FSX, but is there any workaround for FS9?

Thanks for reading this loooonng post!