How do I make xmobar use a different symbol at the start and end of a bar in my monitors?

Question

By default xmobar uses '#' for the foreground and ':' for the background of monitor bars (such as the volume bar). I would like to instead use the progress bar symbols from the fira code font (U+ee00 to U+ee05) which has a different symbol for the start and ends of bars. How would I make xmobar use a different symbol at the start and end of the bar?

I have tried this in my xmobarrc:

(fn=2 is font awesome and fn=3 is fira code)

Run Alsa "default" "Master" ["-t", "<status> <fn=3><volumebar></fn> <volume>%"
                            , "-b", "\xee00\xee01\xee01\xee01\xee01\xee01\xee01\xee01\xee01\xee02"\"
                            , "-f", "\xee03\xee04\xee04\xee04\xee04\xee04\xee04\xee04\xee04\xee05"
                            , "--"
                            , "-O", "<fn=2>\xf028</fn>", "-o", "<fn=2>\xf6a9</fn>"
                            , "-C", "#DEADFF", "-c", "#DEADFF"]

but that resulted in the opening part of the bar appearing in the middle like this: Screenshot of my volume monitor

I want it to look more like this: Screenshot of how I want the bar to look

I hope I have made this post clear enough, I don't know if I used the right words to describe each component but am happy to clarify if it is confusing.