Hello,
I got that texture for a barrel, and the only way I found to have a somewhat “correct” width for the planks of the barrel is to scale (up or down, I am not even sure) one of the UV island. On the barrel, right panel, it looks okay, I guess. But in the UV pannel, we can see that the Island is way outside of the texture.
Nope. Grant explains somewhere in this section that when an island does this, the texture repeats itself. That’s why you don’t have any glaring black areas in your model. You’re good! =)
There is a tick box to Repeat the image in the UV pane N Tool Panel. On the right.
Tick it and it shows the image tiled over the whole pane area.
Gives you the reason why overlapping the marked area is not a problem on properly tiled image textures.