I had a pm from a member asking me about how I fitted my full size spare into my boot so thought I would post the pics and details up here as well.
Firstly my rims is 18x8 and my tyre size is 235/40/18.
I cut off the hard foam blocks on the underside of the boot liner (which used to prop it up above the space saver to make it flat) The boot floor now sits very slightly raised in the middle above the spare wheel.
The wheel now sits in the well right side up (so the face you see on outside of the car). I went and sourced a long bolt which screws into the existing thread to hold the spare wheel in. The bolt has the normal hex head on it and i keep a spanner to fit it to undo it in the little tool sacthel that is in the boot.
Heres some pics for you, I think it gives a pretty good idea of how much raised the boot floor is. I guess if you still wanted it to be really flat you could also go to clark rubber and get a stiff piece of foam cut to size with with a hole cut out where the outside of the tyre sits.
Heres the first one showing the underside of the boot floor where i cut off the bottom of the 3 foam bits
The next two show the rim sitting inside the wheel well. I just have an old towel underneath I cut a hole in for the bolt to go through. I used the existing metal cap thing and a piece of sponge to protect the surface of the rim and the bolt holds it firmly in place. I had to take the original bolt thing into the specialiy nut/bolt place so they could get one which matched the existing thread
The next ones just show the boot floor with the wheel sitting in place to give you an idea of how much the floor is raised in the middle. I would guess its max 2cm (you can see on the bottom of the back of where the seats are the difference between where the floor sits in the middle compared to the edge
Hope this helps Its pretty easy to achieve and the special nut and foam bits if you want them are cheap. You dont even have to have the same rim as your existing ones I guess just the same size and tyre size.
A little bit of non-technical info to help you guys out who have wondered if its possible ... heaps better than having to rely on the silly yellow spacesaver to get you out of trouble a long way from home.