Smaller RetroArch Screen doesn't work

[pinho83]

Pi Model or other hardware: Pi3 B
Power Supply used: original power supply
RetroPie Version Used: 4.7.1
Built From: Pre made SD Image on RetroPie website
Emulator: lr-gambatte

Hi everyone and sorry for my English. I'd like to reduce the screen dimensions of the portable console emulators on my monitor LCD 19'. I read the Smaller RetroArch screen documentation.
With my precedent version of Retropie (4.3.1.2) all works good.
Now I made a new installation (pre made SD image 4.7.1) and I modify the same values (custom_viewport_width, custom_viewport_height, custom_viewport_x, custom_viewport_y) in the file locate in (/opt/retropie/configs/gb/retroarch.cfg), obviously I save the file and so I reboot the system.
But when I launch a game emulator has a full screen video size.
Thanks.

[mitu]

Can you post the complete .cfg file ?

[pinho83]

@mitu Thanks. I think I found the problem.
This is my retroarch.cfg (taked from the previous version of my Retropie (4.3.1.2.):

# Settings made here will only override settings in the global retroarch.cfg if placed above the #include line
input_remapping_directory = "/opt/retropie/configs/gb/"
# 19 = Config, 20 = 1:1 PAR, 21 = Core Provided, 22 = Custom Viewport
aspect_ratio_index = "22"
# these two define the pixel size of the emulated screen
# keep this in the same ratio as the original console
# eg: GBA 240x160 * 3 = 720 x 480
custom_viewport_width = "480"
custom_viewport_height = "432"
# the following two decide how far from the left and top the game screen is shown
# to centre the game display use your original resolution, minus the screen size, divided by two
# this example for 1080p screen (1920x1080)
# (1920 - 720) / 2 = 600
custom_viewport_x = "400"
# (1080 - 480) / 2 = 300
custom_viewport_y = "324"
#include "/opt/retropie/configs/all/retroarch.cfg"

I modify Custom Viewport aspect_ratio_index from 22 to 23 and now screen size is correct.

Thank you very much.