Maker and Black Crystals/Dark Crystals

I was just about to make a thread like this.

1. Dark Crystals add to Str, Dex, Int, Luk ONLY yes
2. Dark Crystals can add or take away from those stats yes, I'm pretty sure it's 50/50
3. Dark Crystals add/take away from all of the mentioned stats present yes, they need to be present. A 1 dex glove can only have dex altered, not str, int, or luk.
4. Black Crystals add to weapon attack, acc, avoid, etc. (basically, all other stats than the four AP ones) nope. That taragon has 3 accuracy (average), when it should have had (2~4)+4 from the crystal. They ONLY affect the four AP stats
5. Black Crystals, like Dark Crystals can take away and add to stats (like the Dark Crystal, in a similar manner to chaos scrolls) yes and no. They can raise or lower by varying amounts, but once that is determined, all (four AP) stats present are altered by that amount. If your dark crystal happened to raise stats by 3, all of the str, dex, int or luk attributes on that equip would be raised by 3.
6. Black Crystals can add/take away attack (similar to 4, but more specific) no, black crystals operate the same way as dark crystal, but they're less powerful (1, 2 or 3 compared to 2, 3, or 5)

I've been thinking that dark / black crystals can alter stats by a range of 1 to 1, 2, 3, or 5. I used an intermediate dark crystal on a 1 str 3 dex shoe, and got it 0 str, 2 dex, which supports this theory (range of 1~3, happened to land on 1). Is there anything definitive on exactly how these work?

 the shoe