overscan in config not adjusting, still got black bar

[rig]

so I was able to move the lt side of the screen over so the text was not cut off but the rt side of the screen still has a black bar. I achieved this by adjusting the overscan settings in the config file of the sd card. I can adjust the config file to make the black bar on the rt bigger but I cant make it smaller. it seems like the cofig file wont recognize negative values. the overscan portion of the config file looks like this

#uncomment this if your display has a black border of unused pixels visible

and your display can output without overscan

disable_overscan=1

uncomment the following to adjust overscan. Use positive numbers if console

goes off screen, and negative if there is too much border

overscan_left=5
overscan_right=-5
#overscan_top=16
#overscan_bottom=16

why won't my pi accept negative values for the overscan?

here's my setup
I have a rpi 3 outputing analog rgb via gert 666 to a UMSA that outputs to my pvm2030;
I downloaded the bulid sdimage from retropie version 4.1;
the config code I used for to output 240p is

dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
#hdmi_timings=336 1 10 30 34 252 1 15 3 42 0 0 0 50 0 6400000 1 # 336:252 6.4MHz progressive
#hdmi_timings=336 1 10 30 34 252 1 15 3 42 0 0 0 50 0 6400000 1 # 336:252 6.4MHz progressive
#hdmi_timings=256 1 6 17 18 192 1 26 22 29 0 0 0 60 0 4800000 1 # 256:192 Sega Master System (NTSC)
#hdmi_timings=256 1 8 17 21 224 1 7 10 24 0 0 0 60 0 4800000 1 # 256:224 NES, SNES (NTSC)
hdmi_timings=320 1 20 29 35 224 1 10 14 16 0 0 0 60 0 6400000 1 # 320:224 Sega Genesis (NTSC)
#hdmi_timings=320 1 14 46 28 256 1 17 32 9 0 0 0 50 0 6400000 1 # 320:256 Amiga (PAL)

ps. I do not want to adjust the pots inside my pvm; I have the pots just where I want them for all the original hardware (nes, snes,etc) I have hooked up

pps. I have tried adjusting the x and y settings under the video settings of retroarch but it doesn't seem to do anything