He wrote me back and said:The tandem in the video is a homebuilt one by my father (who filmed btw. while I was on the captain's seat). You can see it on my webpage http://radseiten.die-andersecks.de/lieger.php (Rücken-an-Rücken-Tandem).
We had the building instructions of the Flevo-BTB here but eventually it had some disadvantages for us:
-big wheels are less stable-the suspension in the middle doesn't bring the wished effect anyway, therefore we chose mesh seats and wide tyres
-the Flevo-BTB is not very stiff when doing fast changes of left and right corners. It bends somewhat in the middle. Our tandem doesn't do that so extremely.
-once built you cannot modify so much at the Flevo-BTB, no easy luggage carrier in the middle and that stuff. Therefore the simple steel tube (50x50x1.5mm btw.).
The BTB concept isn't very popular because recumbent cyclists are "strange" people. And for a tandem you need two of them cycling together regularly. Our tandem was mainly thought for my parents but of course it's much fun to go on it with two strong cyclists. I've done a 24h race together with a friend of mine which was really great fun.
This is the second person with a Flevo BTB who reports that the frame has too much flex in turns. Dustin Anderson reported that the Flevo he bought used had this problem but that it was caused by the fact that many of the small rivets in the aluminum skin on his bike had backed out or failed. He replaced all the rivets but I don't have any ride reports from him so I'm not sure I fixed the problem. I've never experienced the problem on my Flevo, but I bought mine with very low mileage.
I do have to agree with Martin that the smaller wheel size makes the bike much handier to start and maneuver.
