Love this!!!! It's so cool to play Big Race USA on my virtual cabinet! Right now, the backglass is also showing the DMD. My cab has a real DMD though (PinDMD3) - is it possible to display the DMD through PinDMD, or is it only possible to show on the backglass monitor?
Thanks 
the launcher checks your screen configuration.
By default:
- if you have 2 screens : the DMD will be shown on your 2nd screen and the backglass grill will be displayed if your 2nd screen ratio is less than 16:10.
- if you have 3 screens :
* If your 2nd screen ratio is 16:10 or above : the DMD will be displayed fullsized on your 3rd screen
* If your 2nd screen ratio is less than 16:10 the grill will be displayed and the DMD will be shown on it (nothing in 3rd screen)
(with 4.1 version you can set NoGrill option to hide the grill and to display the DMD on your 3rd screen)
So if you have only 2 screens I fear you won't be able to hide the DMD from the backglass but you can still mirror it to your DMD device (you will have 2 DMD display)
With a DMD device, the best solution would be to add an hidden 3rd small and cheap screen (an USB one for example) and that way the DMD will be put on it and you will be able to mirror the dmd display to your dmd device 
Hope it helps 