I'd say whatever works. Since it sounds like neither of those work, you can try to pick up a replacement starting cone that has a smaller cone-shaped opening that better fits your spinner nut. Or you can replace the spinner nut with something that fits the cone better.

On thing about the vibration, no matter which way you have things, if the starter is out of alignment with the crankshaft, you get that vibration. Try moving your hand around to change the angle of the starter to the engine, you might find the vibration suddenly goes away.

As a side note, you usually shouldn't find yourself cranking away with the starter motor anyway. If the engine doesn't start pretty quickly, there is usually some other issue. (usually just as simple as priming the engine first).