I was wondering if there is physical space to install a 2.5 inch drive, along the supported M.2 drive in a 10i7FNK? I know there is no tray, but I was wondering whether a solution like gluing a 2.5 inch drive to the bottom cover, or similar, would be supported by the physical space available? I have a proper SATA and power cable.
Sorry, but this is simply not possible. There is not enough room in the 'K' chassis for a 2.5" drive to be installed. You need the taller 'H' chassis in order to do so.
P.S. Somewhere, I saw plans for a 3D-Printable chassis extension ring. You could look into that if you have access to a 3D Printer.