That's what I've been doing but it seems like a "work-around" rather than the correct way. I also think that the flavor is different if done this way.
I wouldn't call it a "work around" as it is the most efficient way to get the exact level of sweetness you want while keeping the ABV at a level you like. It also allows you to get the benefits of using yeast that may have an ABV tolerance much higher than you'd like.
Still, if you don't want to use backsweetening, there are some other options. For one, you can "cold crash" the mead at the desired gravity (as long as you know at what point you like it best). You put the active fermentation in a fridge near 32 F and let it sit for a couple of weeks. The cold will put the yeast into hibernation and much of the yeast will precipitate out. Then rack it (while cold) onto sorbate and sulfite, and the yeast should stay dormant.
You can keep feeding the yeast honey until they quit, but this "step feeding" tends to push yeast beyond their usual alcohol tolerance, and may create some very harsh flavors.
You can try starting with a gravity that is higher, and D47 can work with a gravity of 1.140, but typically that will leave the gravity around 1.035 in most cases. I've found that D47 usually stops around 14% for me (with the exception of a few cases such as apple cysers). Perhaps if your provide the details of your recipe and process, we can understand why you are having D47 take batches dry from 1.120 - that's a little unusual.
You can also go with a yeast that has lower ABV tolerance to keep the alcohol down. A good ale yeast can typically keep it to 10-12%, but if your recipe causes consistent overshoot, it might go a bit higher (perhaps 13-14%). Another alternative may be a change to something like 71B, or another wine yeast with 13-14% ABV yeast that will be less likely to overshoot to 16%.
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