OK, I have some updates.
1. Tank 2 has been going hard within the last 30 gallons or so, so I increased H to reduce my regen point from 295 to 266 gallons. Under the new settings, the hardness stays below 3gpg to the regen point. I'm not sure if changing H was the best solution, or if I should be increasing the brine fill, or a mix of the two. Too bad I can't individually adjust the tank settings.
2. Stupid me failed to take a look at the media level when replacing the valve heads. I'm guessing that tank 2 has less media. Can I add a bit to tank 2 to top it off? I don't know how much this stuff costs, what type I have vs. what to buy, etc, but would love to be go back to 295 gallons. Even with the reduced capacity, I am using close to HALF of the salt that I was with the Kinetico.
3. I do occasionally get hard water toward the end on both tanks, and I think I have traced this down to a defective (Wellmate/Pentair/Whitewater CH5551) air bleeder (in air-injection-based sulfur removal system that precedes the softener) that sometimes gets stuck closed. It has done this since I installed it a year and a half ago. That's what I get for not just cleaned the old one lol. I believe that the sticking vent allows non-vented air to collect in the "in use" softener tank to the point that incoming water will "tunnel" through a portion of the media, rather than uniformly down-flowing, thus depleting the media that gets overused. Anyway, I am getting a warranty replacement vent in a week or so.
4. To ELIMINATE air in the softener tanks, I've been considering drilling a 1/16"-1/32" hole in the side of the riser tube inside the upper baskets, or in the distributor adapters. That way, air that enters the tank would make its way out through the small hole. The biggest issue I see with this idea is that my water is so hard that the water that passes through that hole (when air isn't) could measurably increase the output water's hardness. The small hole might be prone to clogging as well.
5. The Fleck seems to demand less water flow rate during regen as well (I hardly notice it's happening now), so the night time regen isn't nearly as important to me. Hopefully the backwash/rapid rinse are strong enough to do the job in the longer term with my water.
Though I still have some work to do, even as it stands right now, I am waaaay happy with this new setup relative to the old one.