Well typically any fruit that comes in with a high pH like that we adicify, sometimes before primary and sometimes after both primary and secondary. Since we never pick reds below 25 brix, we see this a lot. We do however leave some wines around the pH 4.0 range though. They tend to be very easy to drink. Very soft, very rich in flavor, dark fruit characteristics dominate, zero vegetal character but also they tend to lack the mouth watering acidic tang I tend to enjoy in some wines.
The biggest factor though is the brix. At that pH, you probably have high brix. Like 26-30 brix. So alcohol is an issue. You either water back and get those brix down, or leave it and have a 16% alcohol. We do slight waterback as to not dilute the flavor, but the alcohol still stays up there in the 15s.
As far as stability goes on those wines, we keep our molecular SO2 as high as we can within reason during aging. It's hard to get to 0.5 or 0.8 ppm molecular so2 though, that takes a lot of sulfur at pH 4.0. Top the barrels regularly. We keep our barrels insanely clean, our equipment clean. The barrel room that we age in is cold which important. 54F max. Then finish off with sterile cross flow filtering a few days before we bottle it. Bam, stabile pH 4.0 wine.