This is the final answer you are waiting for. I bought a hdd caddy 12.7mm (
http://hddcaddy.nl/winkel/#ecwid:category=1735048&mode=product&product=7407869)
This was the perfect size for my laptop (ASUS x77jq)
When I got the hdd caddy it was little but difficult to get the cd-rom out of my latop because the amount of screw. But I got after hour. I also remove the plastic front of the cd-rom and put it on the hdd caddy. That why you don't is that it's change.
I have put my harddisk in the hdd caddy and everything work fine.
For you all, I was surprise how good the harddisk fit in the caddy. The harddisk has no space to go anywhere so nice it fit in the caddy.
My experience this that a hdd caddy a good way is to get a SSD/second hdd in a old laptop.
Hope this make more sense what I have done and what my experience was.
If something is not correct type or you want to now more. I will follow this thread for a little while longer the answer you questions.