In answer to the potential half wave AC flicker issue, I whipped up a fast SMD re-design with a bridge diode, 47uF cap, and a 1210 size load resistor R1. It worked out quite well, and the board stays the same nice compact size. Here she be:
The little bridge diode is an SOT-123 size (good for 200ma) and would be the most challenging part to solder. I just happen to have a few of these in stock, so that's handy, same for the little caps. The 1210 size resistor is easy to solder, and the size means it is good for 1/4 watt. You can also use as small as an 0805 size with the same board pattern, but it will be only 1/8 watt. Note that depending on the circumstances you could install the leds through from the other side of the board just as easily. The three smd parts though have to stay on this side of the board because, well, they are surface mount.
This board would eliminate any potential AC flicker, real or imagined, and also would help with any center rail voltage dropouts. I wish I had other boards to order right now so I could add a few of these to it. But my latest board order just shipped today already. Drat, bad timing. Might look at getting a batch of assembled boards done with a load resistor sized for 18vac track power. It can easily be changed if needed.