When allowed to warm up, the voltage settled at a slightly higher level than the initial quick test I did without a heat sink. It starts at 20.4v after  a couple of seconds is 20.5v after 10sec is 20.6v and after  a minute is 20.7v were it remained even after several hours. When running at either 33 or 45rpm it remains a constant 20.7v, if considerable finger pressure is applied to the rim of the rotating platter the voltage remains at 20.7v. If you keep increasing the pressure, eventually the voltage drops off to around 18v but you are talking a lot of pressure and just before the point where the motor stalls. On start up for 33rpm the voltage drops to approx 20.5v for half a second, but this is inconsistent and on some occasions did not drop at all. On start up for 45rpm the voltage drops are also inconsistent some times as low as 19.2v sometimes around 20.2v again for about half a second. If you do quick start stops the drop seems larger, if you allow a pause, about the time to load a record the drop is smaller, maybe the capacitors are playing catch up. Also when stop is pressed there is a momentary drop of 0.1/0.2v as the brake is applied. For all these tests I had the stock platter, a 180g record and a 800g brass puck in use.  All in all I think this power set up is pretty stable.