Plop And 4-in-1 Card Reader

[SMurf]

Hello,

I am trying to boot via a 4-in-1 card reader.  When I attempt a USB boot via Plop, it sees the SD card slot on the reader and attempts to load the boot sector from it.  This slot is empty(!).  The process freezes at "Loading boot sector".

My bootable card is inserted into the CompactFlash slot (slot 2).

If I insert a random SD card into the SD slot and try booting it continues but shows a blank screen with a flashing cursor in the top left corner.
If I try booting using <Ctrl>+U and selecting N on finding the SD slot it doesn't find any other devices.

As far as I am aware this is not a hub, it appears in Windows as four removable disks.  The instance ID of the drives looks like 058F312D81B&0, &1, &2, &3.

Is there a way I can encourage it to look at the second slot?