question

To first order, all the data we have show that LiFePO4 batteries’ lifetime capacity improves when run at lower states of charge most of the time, with an occasional run up to the top as you mention.

If you can find a combination of settings (voltage, absorption time) that will place the cells somewhere more in the range of {70%, 90%} or even {60%, 80%} you will probably extend their life somewhat. You definitely have that luxury since you don’t expect to draw them down very far, very often.

One downside is that current-based state estimation, like what you get from a BMV, will tend to drift if you never reach a full charge. But when you do charge to 100% once a month or whatever, it will synchronize back and be accurate once again. How fast it drifts, and whether someone cares about having that last bit of accuracy, will vary.

I do not know the answer to your question about borrowing the equalization feature to do the top-balancing charge. It sounds like a good idea, though.

The last thing I would mention is that there is no guarantee that your solar supply can take the batteries to 100% with a long absorption curve. Some setups need another charge source (marina, shore, generator) to make this happen reliably.