Has anyone tried reducing the abv by diluting the finished product with regular store bought grape juice like Welch's? I'm looking to make a slightly sweet red with an abv somewhere in the 8 - 10% range.
I believe a lot of people on the forum do this. Be sure to stabilize the wine with K-meta and K-sorbate before adding the juice to prevent re-fermentation.
I use Welches concentrate to back sweeten frequently. More to raise to a desired sweetness and to add flavor. If you like the flavor before back sweetening,, be aware concentrate is going to change flavor more than a juice or even a sugar/water addition (which will add sweetness without additional flavorings).
As Long as you are stable as Rocky mentioned and your intention is to reduce alcohol content whatever you use is just a proportional dilution to your initial finished ABV. Formula available if you want (email easier) as it is in an Excel file (with examples).