I have found a solution thanks to this post: https://forum.dcs.world/topic/134049-3-monitor-setup-moving-all-radio-texts-to-center-screen/?do=findComment&comment=2725156
For anyone interested with the resolution of my main monitor being 2560x1440, you have to modify this file C:\Program Files\Eagle Dynamics\DCS World OpenBeta\Scripts\UI\gameMessages.lua on line 117:
main_w, main_h = Gui.GetWindowSize()
main_w = 2000 (add this line, I think its the total width where the messages will be displayed)
window:setBounds(300, 400, main_w, main_h) (300 will be the left spacing, and 400 the upper spacing)
I dont know how to code so maybe its wrong, but its working.
Seems to pass IC with no problems as the other one.
malarcky's post in Move radio messages and mission messages lower and right/left was marked as the answer