The ball joint example is not a good choice , you can hit the puller very close to the taper. With the flywheel not so. I´d think any hit on the rim will spread the shock wave into the whole component and not much arrives at the taper fit and the hit will be waisted. First step for an effective puller device would be two bigger threads in the flywheel to take the higher loads from the puller into the assembly. So then one or two hard whacks on the puller center should free the lot. I have never had to do otherwise on the BMW parts, not even thinking of hitting the rim. My guess, the Douglas taper is smaller than the 35mm size on the Earles BMW, but possibly the angle of the Douglas taper is below 5 degrees and hence the troubles with it, a design mistake then.
Vic
Vic