Just add the NESTING option to adjust subscreen width (no horizontal scrolling) - subscreen size
SELECTION-SCREENBEGINOFSCREEN100AS SUBSCREEN NESTING LEVEL 1.
Increase the number of lines, height, of the tab block (no vertical scrolling) - subscreen area in main dynpro
SELECTION-SCREEN: BEGINOF TABBED BLOCK mytab FOR16LINES,
Regards,
Raymond