How to make the selectInput choices in Shiny extend beyond the well panel or otherwise make them more viewable by the user?

In running the example code posted at the bottom, the viewing of the selectInput() choices are obscured by the bottom edge of the wellPanel(). You can see an example of this obfuscation in the below image. The user has to fiddle with the mouse wheel to view all of the input choices. In the full code this example is deployed in, the problem is worse than in this example in getting the right-most selectInput() choices to render for the user's viewing. Is there a way to get the choices to extend below the wellPanel(), or to otherwise address this quirk?

The wellPanel() needs to scroll along the x-axis the way it currently does, and I don't want a huge wellPanel() that far exceeds the size of the selectInput() boxes when they are dormant. The below formats nicely when the selectInput() boxes are dormant; there are no huge empty margins. The only problem is when the user tries viewing and selecting the choices.

Example code:

library(shiny)

ui <- fluidPage(
  br(), br(),
  wellPanel(
    style = "overflow-x: scroll",
    splitLayout(
      column(
        12,
        selectInput("i1", "I1", c("Boy","Cat","Dog","Rat","Bat"))
      ),
      column(
        12,
        selectInput("i2", "I2", c("Boy","Cat","Dog","Rat","Bat"))
      ),
      column(
        12,
        selectInput("i3", "I3", c("Boy","Cat","Dog","Rat","Bat"))
      ),
      cellWidths = "40%"
    )
  )
)

server <- function(input, output) {}

shinyApp(ui, server)

Nice:

ui <- fluidPage(
  tags$head(
    tags$style(HTML(".selectize-dropdown {position: unset;}"))
  ),
  br(), br(),
  wellPanel(
    style = "overflow-x: hidden",
    splitLayout(
      ......