Thanks guys for the suggestions.
Although I still have problems my issues earlier should be ignored. Apologies - I still had the old config file to position the DMD and it seemed to be using it as I had the window border.
----- PinDMD1 test -------
I therefore started again, and updated to the latest Pinball FX2.
Now if I set the dmd size in the game cabinet options to 1040 x 272, I get nothing on the DMD like rockyrocket.
I also tried the gray4 option.
The test image works for me, as does the screen mirroring.
However, if I change the DMD size in the game to 800 x 200, I get some graphics displaying but not fully. I guess this is due to the window being the wrong size. I experimented with a lot of values and sometimes needed to restart dmdext. 900 x 200 also displays something. Here are some photos.

Behaviour with those settings (if video help I can do one)

Rocketrocket - it would be interesting to see if you get the same behaviour with settings for the DMD of 800 x 200?
Edit: Video added with the 800 x 200 DMD size (1040 x 272 doesn't show anything):
https://www.dropbox....1_Test.mp4?dl=0
Thanks
Edited by atarian, 24 April 2016 - 03:11 PM.