Monoborracho, indeed remain concerned about the set-up. When I got the bike last December, I did measure the steerer with calipers and found that it was consistent up and down its length. Spacers and stems all seem to be fine. Ideally I would like to find a stem bar combo that would work with maybe a longer steerer (new fork), but in working the geometry and available stems on the market, there really are not many options. Moreover, pretty hard to sort out from here.
The lack of headtube height was the biggest surprises for me with this bike. Have never needed such a device before in decades of cycling and the bikes to go along with it. It was a long search (due to my size) that led me to this jumbo-sized Cannondale and Tandems East, and when I was actually told that I would need such an extender I was a bit surprised. But given the dealer, like others here, said they're often used, I just went with the flow as we were glad to finally have secured a bike before the end of my last stay in the US. Maybe I should try to locate a Zoom Heads-up or some other brand of extender and see if that offers better grip.