So this is now a one day old battery. First of all, it DOES start the car! That's an improvement over the other one.
At idle I'm getting roughly 14.55 volts. At 2000rpm it goes up to roughly 14.65.
I've been removing the negative cable at days end to eliminate the draw from that ongoing red light.
As the previous battery was failing, the spoiler was raising as soon as I started the car. That's NOT happening now. I've not had it out anywhere with the new battery in place to get up above 60mph to make sure the spoiler goes up on its own.