Hackers Help: How to make this triple bunk bed?

Hello everyone,

I am new to both this website and Ikea hacking in general, but a big fan of some of the Ikea hack ideas I’ve seen!

I am looking for some assistance to build this:

triple bunk bed

I was thinking that I can use two KURA beds to make the top and middle bunk and just place the bottom mattress on a plank of wood on the floor. What I am not sure of is how do I elongate the KURA to make it a top bunk?

Any suggestions would be most appreciated!