So, for your Main and Stage Displays, we recommend setting those to 1280x720 within Windows. Then, within MediaShout, under Settings > General Settings > Cue Setup, set the Resolution to 1280x720 to match the Windows Settings. Then, go to File > Repaginate to resize your current script.
That should allow the text to not be cut off.
Just in case, here is an article that walks you through this process: https://support.mediashout.com/808569-Setting-Up-Screens-in-MediaShout-Version-6-Windows--Mac
I hope this helps.