I recently went to my local auto parts store (Pep Boys) and bought some of that window tinting film that you can put on your car windows. It comes in three grades of VLT = variiable light transmission: 35%, 20%, and 5%. The 5%, also called "extra dark limo grade," allows only 5% of the light to be transmitted, i.e. it blocks 95%. I cut a small rectangle of the 5% and taped it so that it covers the R-09 screen. I tested it out the past two nights. In a dark stealth situation, it was just bright enough for me to be able to see my meters and other info on the screen. Others might prefer the 20%... with the 20% film the screen would be brighter but still only a fifth as bright as the current "darkest" setting on the R-09.
The film comes in a large roll for $9.99. I would have preferred to get a smaller portion... I only needed a few square inches (I also used it to darken my digital camera and camcorder screens) and now I have a huge roll left over. Oh well, it might come in handy one of these days.
Apologies if this has already been mentioned and I missed it. I actually got this tip from the photo/video forum a while ago, thought I'd mention it here as it worked well for me this past weekend.