After investigating how to install a front to rear cable whilst trying a twin dashcam (now sent back!) - I eventually discovered (by mistake) that it is possible to remove the fixed base (firm lift up at the front of each side and slide forward and out) giving a much flatter load area with rear seats folded. (I suppose I should have bought the Combi where the seat base tilts forward)

 

Why is this not shown in the user manual?

TBH whilst it works (and I have done it ocassionally) I suspect that it is not really recommended as eventually the foam seat bases, (which are not protected) will wear, become damaged and will no longer be gripped securely.

I checked mine when I first got the car as the one's in the Fabia vRS swivel up and forwards so the backs lay flat when down etc... I couldn't get the bases to move in the Superb but I put that down to it having heated rear seats and didn't try too hard as I didn't want to damage the heater elements or wiring. I've had the rear seats down a few times to transport stuff and it's never caused any issues as yet with them not going down fully flat.

I did it once in 3 yrs of ownership. One large trip to IKEA and I needed all the space! It was a pain though and not the easiest thing to do. Required a bit of fart arsing around to get it back proper too.

Today I converted my twin door into a student removal van by removing seat base (much easier second time now I know how), rear head restraints and parcel shelf. Got huge amounts in including PC , amp and bookshelf surround speakers in the footwells