Layout to ShinyUI with Custom React adding Unwanted Border

Working on an R Shiny web app which using React and custom CSS library. All works well, but I also need benefit of UI Definition such as fluidPage . When I add fluidPage , my App gets about a 30% blank border around the App. I'm looking to have that border removed so content extend to edge of screen.

# this code looks great without the border
shinyUI(
    custom_react_page(
      app_structure(
        navigation,
        footer = pages$footer,
        switcher(switcherId = "theme", onText = "Light", offText = "Dark",
                 label = "", defaultState = ifelse(default_theme == "dark", "off", "on"))
      ),
      theme = paste0("theme-", default_theme),
      useShinyjs(),
      tags$link(rel = "stylesheet", type = "text/css", href = "css/sass.min.css"),
      tags$link(rel = "stylesheet", type = "text/css", href = "https://cdn.jsdelivr.net/npm/intro.js@2.9.3/introjs.css"),
      tags$script(src = "js/filter-toggler.js"),
      tags$script(src = "js/strategy-breakdown-toggler.js"),
      tags$script(src = "js/particles.js"),
      tags$script(src = "https://cdnjs.cloudflare.com/ajax/libs/intro.js/2.9.3/intro.min.js")
    )
)
# this code adds the 30% blank order around the App.  Only thing is adding the fluidPage
shinyUI(
  fluidPage(
    border = 0,
    custom_react_page(
      app_structure(
        navigation,
        footer = pages$footer,
        switcher(switcherId = "theme", onText = "Light", offText = "Dark",
                 label = "", defaultState = ifelse(default_theme == "dark", "off", "on"))
      ),
      theme = paste0("theme-", default_theme),
      useShinyjs(),
      tags$link(rel = "stylesheet", type = "text/css", href = "css/sass.min.css"),
      tags$link(rel = "stylesheet", type = "text/css", href = "https://cdn.jsdelivr.net/npm/intro.js@2.9.3/introjs.css"),
      tags$script(src = "js/filter-toggler.js"),
      tags$script(src = "js/strategy-breakdown-toggler.js"),
      tags$script(src = "js/particles.js"),
      tags$script(src = "https://cdnjs.cloudflare.com/ajax/libs/intro.js/2.9.3/intro.min.js")
    )
  )
)