Re: edid vs. modeline
Yes, I have thought about that but it seemed like a hack.
So, I captured the edid.bin from the working DFP and use it with the CustomEDID option on the 3dp. It works, as expected, and gives me a 1280x1024 at 60Hz display.
How would I now go about adding on a 1280x1024 at 105Hz display, or any other mode which the DFP does not support ? The 3dp (and the projectors behind it) can show that using another image backend.
The first step may be to replicate the working mode (1280x1024 at 60Hz) but without edid, in a custom modeline. How would I do that ? Use xvidtune, or the edid timing information as reported in the Xorg.0.log ? That did not seem to work, eg. resulted in a refusal to accept input or to provide output (black screen).