That's a cool setup! I like the overlayed gauges - I may have to give that a shot. I will post up a screenshot of my setup once I grab it at lunch if I remember.
Oh if you want the "KR" value to switch the meaning of negative and positive I found a way to trick it. You can't multiply by a negative in the formula or it gives you a "stack error" but you CAN trick it by putting in "-1" in the English to Metric conversion factor. That will result in Negative readings for taking away timing and positive readings for actual knock.