this is my /opt/retropie/configs/gb/retroarch.cfg

# All settings made here will override the global settings for the current emulator core

video_shader_enable = true
video_shader = /opt/retropie/emulators/retroarch/shader/bead.glsl

input_overlay_enable = true
input_overlay = /opt/retropie/emulators/retroarch/overlays/gb.cfg
input_overlay_opacity = 0.70 # 1.0
input_overlay_scale = 1.0

aspect_ratio_index = "22"
custom_viewport_width = "645"
custom_viewport_height = "648"
custom_viewport_x = "637"
custom_viewport_y = "275"

which gives me the picture attached

Just curious what settings you’re using? I don’t see too many people using RetroArch shaders and overlays. To be fair, I tried on on the Pi 1 but performance suffered too much. With the Pi 2 I’ve been trying them again.