Para resolver el tamaño de tus ALVs y que se ajusten a la ventana sin necesidad de pintar los custom_control en el Layout... En el PBO de tu dynpro:
*---> Generar el container.
CREATE OBJECT g_doc_cont_cntrl_new
EXPORTING
side = cl_gui_docking_container=>dock_at_left
extension = 10000
name = 'CONT_CNTRL'
EXCEPTIONS
cntl_error = 1
cntl_system_error = 2
create_error = 3
lifetime_error = 4
lifetime_dynpro_dynpro_link = 5
OTHERS = 6.
* Espacios en pantalla donde habrá contenedores --> Elige una de las 2 formas
---------------------------------------------- (horizontales)
CREATE OBJECT g_splitter
EXPORTING
parent = g_doc_cont_cntrl_new
rows = 1
columns = 2.
--------------------------------------------- (verticales)
CREATE OBJECT g_splitter
EXPORTING
parent = g_doc_cont_cntrl_new
rows = 2
columns = 1.
----------------------------------------------
*---> Tamaño de los contenedores -----> CON ESTO LE DAS EL TAMAÑO
CALL METHOD g_splitter->set_column_width
EXPORTING
id = 1
width = 20.
CALL METHOD g_splitter->set_column_width
EXPORTING
id = 2
width = 50.
*---> Contenedor ALV
CALL METHOD g_splitter->get_container
EXPORTING
row = 1
column = 2
RECEIVING
container = g_container1.
CALL METHOD g_splitter->get_container
EXPORTING
row = 1
column = 2
RECEIVING
container = g_container2.
*---> Creación de objetos
CREATE OBJECT grid
EXPORTING
i_parent = g_container1.
CREATE OBJECT grid
EXPORTING
i_parent = g_container2.
Sí quieres te dejo por aquí también las variables --> Añade las que necesites
DATA: g_custom_container TYPE REF TO cl_gui_custom_container,
g_doc_cont_cntrl_new TYPE REF TO cl_gui_docking_container,
g_splitter TYPE REF TO cl_gui_splitter_container,
g_container1 TYPE REF TO cl_gui_container,
g_container2 TYPE REF TO cl_gui_container,
grid TYPE REF TO cl_gui_alv_grid, "ALV
grid2 TYPE REF TO cl_gui_alv_grid. "ALV