In setting up dual monitors for Helios DCS World requires you change the display options.
Tutorial.lua is the monitor configuration file.
Resolution and Aspect Ratio in the DCS World options page are TOTAL x and y ie width and height of your combined monitors, this info will be saved in your options.lua file.
If an invalid configuration (monitor.lua) makes it difficult to start DCS World you can edit the options.lua file to reset it back to a configuration that works.
I will add to the previous posit.
More tutorials here: Below are some Helios tutorials using both DCS Warthog, BlackShark and BMS Falcon as examples:
Basic Helios Tutorialhttp://simhq.com/forum/ubbthreads.php/topics/4311178/Basic_Helios_tutorial_w/_RWR_i#Post4311178Showing Helios Control Panel and Helios control of DCS Active Pausehttp://simhq.com/forum/ubbthreads.php/topics/4313084/Helios_Control_of_DCS_Active_P#Post4313084Helios Panel Creation Method 1 (cockpit design)http://simhq.com/forum/ubbthreads.php/topics/4312789/Helios_Panel_Creation_Method_1#Post4312789
Helios Panel Creation Method 2, the Best Method (cockpit design)http://simhq.com/forum/ubbthreads.php/topics/4312877/Helios_Panel_Creation_Method_2#Post4312877Getting Screen Coordinates of Windows without use of graphics program (cockpit design).http://simhq.com/forum/ubbthreads.php/topics/4313980/Helios_easiest_way_to_get_scre#Post4313980
Helios Gotchas for the Noobie (cockpit design)http://simhq.com/forum/ubbthreads.php/topics/4313906/Helios_Gottchas_for_the_Noobie#Post4313906
Helios use of "Send Keys" to Control DCS (cockpit design)http://simhq.com/forum/ubbthreads.php/topics/4312967/Helios_use_of_Send_Keys&#Post4312967
These tutorials use Capt_Zeen's, Ice's Profiles.