I have two dance pads. When I set the global audio sync/offset with one pad I get -0.032. When I do it using the other pad I get -0.002. Even though it is just 1/30 of a second, the effect is very reproducible over multiple tries and for both my son and me. Is there a way to set different offsets for the two pads? Right now I edited the preferences file and set the offset half way between them. Thanks.
That's the best you can do, SM doesn't have anything for dealing with input latency on a per-controller basis. The good news is that they're within a frame of being correct, which is still (just) within the fantastic timing window. I'll make a note of this for SM6 on the bug tracker.
I can verify two different circuit boards can have different latency. All of them are a little different, some have capacitors / resistors, some are super fast at responding. I've always advised using two of the same control boxes for stepmania.