Acid feeders are typically installed after the filter but before the SWCG.
Before you go through an expensive modification, try lowering your TA first to see if you can stabilize your pH rise. Try to target the low end of your TA range (~70ppm) and see if you can get a stable pH in the 7.6-7.8 range. If you can't stabilize your pH rise by lowering to 70ppm, then try going lower to 60ppm and adding 50ppm borates. 50ppm borates creates extra buffering capacity against rising pH and cuts down the pH rise inside your cell by as much as half.
If all else fails, you can the acid feeder but they're not cheap and, like any extra piece of equipment, require maintenance and are prone to peristaltic pump failure (being near a large pool of corrosive acid).
My suggestion is you spend your first season "learning" about your pools chemistry needs before making any major changes.
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