I just picked up my Cargo Box at the weekend. I paid £109 for it, shame I couldn't have got it as a £50 option (along with a couple of other extras), but I didn't want to wait the 8-12 week delivery time when a good deal was available on a 1.2 Lounge that was in stock!
I bought it to store a couple of essentials that would normally be rolling around in the boot. I also liked the idea of a flat loading area. Its a bit deeper than I imagined (and therefore reduces capacity a bit) but on balance I think its worthwhile.
When ordering it, it wasn't clear if it came with a replacement floor/cover of if you used the carpet that is already there. Thankfully I can conform that it comes with new lid/cover that I think will comfortably take the weight of your german Shepard.
The only negative point is that the lid is located on a very flimsy "tag", made of the same expanded foam type material as the rest of the box (and the tyre repair kit holder), and unfortunately this had become broken in transit. The parts technician has already ordered a replacement! In normal use, I think (hope) it shouldn't get damaged.