It should be possible.....someone has put them there.
I think that you have started at wrong end.
Put front side back at her place and start at rear lower end.
You need to pull lower edge that lies on wheel arch into the boot and then slowly take it out from rear pillar by pulling down to the floor.
I did not have them on my R4 but i am making it.
JonathanT send me AutoCAD template and i have made it from cardboard. And tried to put and remove it few times.
Cardboard is easier to bend but this is the way i have done it.