I had the pleasure of travelling up to Germany yesterday and purchasing a trunk extender from Mr Wolfgang
What a nice young guy!
He installed it for me and we chatted about i3's for ages. He knows a hell of a lot about these cars. Mine is a early production unit and he crawled all over it showing me the differences between mine and later produced units. Wish I could have stayed longer and talk more with him, but it was a 1100km one day round trip for me and I had to keep moving. Wolfgang now has his second i3, a 94aH i3s and it looked the business i can tell you. He clearly uses it hard on those German Autobahns!
The trunk extender is really cool and exactly what I was looking for. It's more space that's otherwise not used, great addition if you have a BEV.
Links to images of my instillation here.