Years ago, when I used to build and race recumbents, I built a SWB that I used an original Raliegh Chopper front wheel & tyre in for the first outing, as I didn't have a brake that would work with the intended wheel.
On this set up, I could ride laps of Herne Hill velodrome, no hands!
When I put a lighter, narrower and slightly bigger wheel in, and a better headset, it got into a shimmy when I tried to ride hands off.
Maybe running a heavier dymano wheel in your bike was having a similar damping effect which gave a better feel to the steering?
