How to make tabItem htmlOutput/uiOutput fill the whole page

I've looked at some similar questions, but haven't had luck with other solutions. I am trying to have the uiOutput/htmlOutput of a tabItem in Shiny Dashboard show a full network from the package netCoin. I can't figure out why this won't fill the whole tab frame . Reproducible example below:

library(shinydashboard)
library(netCoin)

ui = dashboardPage(
  dashboardHeader(title = "Example"),
  dashboardSidebar(
    sidebarMenu(
      menuItem("Example", tabName = "example", icon = icon("user"))
    )
  ),
  dashboardBody(
    tabItems(
      tabItem(tabName = "example",
              fillPage(
                tags$style(type = "text/css", "#fullpage {height: calc(100vh - 80px) !important;}"),
                uiOutput("fullpage")
              )
      )
    )
  )
)

server = function(input, output) {
  output$fullpage = renderUI({
    frame <- data.frame(A = c("Man; Women", "Women; Women",
                              "Man; Man", "Undet.; Women; Man"))
    data <- dichotomize(frame, "A", sep = "; ")[2:4]
    C <- coin(data) # coincidence matrix
    N <- asNodes(C) # node data frame
    E <- edgeList(C) # edge data frame
    net = netCoin(N, E) # netCoin object
    shinyCoin(net)
  })
}

shinyApp(ui, server)