I've done this a lot, something like 1kg in 20 litres to answer the direct question. I don't do it now for a couple of reasons.
With fruit in the primary, I became quite uneasy about having fruit sitting around for a couple of weeks at 20 degrees quietly rotting. It didn't look great when it came out. I have no way of pasteurising and infection was a real worry. It did deliver the look I wanted but the sweetness wasn't there at all so it didn't do what I wanted.
Also, here in the UK, cider with fruit other than apples and pears is taxed as a 'made wine' and becomes a very different product. The tax break comes at 4% ABV and left to its own devices to ferment on fruit it comes out somewhere in the 6% region.
When I make fruit cider now it gets juice, 20-25%, at packaging time. I've found that it wants to carry on fermenting in the bottle/keg/box when I do that so that's worth being aware of too.