Thank you, everyone for the positive comments. No thumbs were harmed but there were burning ears from the experience!

I'm sealing in the nail head decals now with a couple coats of Future. A few more comments about them. They are an HGW product printed on (under) a continuous sheet of decal film, so the strips have to be cut individually. They are covered with another sheet of paper material. The instructions would have you cut and apply like any other decals and then after 6 - 8 hours of drying, remove the top paper layer. I found this top layer completely useless. When you cut strips of the nail heads, the top layer just separates and falls away. I used both scissors and a sharp hobby knife to cut the strips. It also hinders placement of the nail heads because it is difficult to see through it.
As I mentioned earlier, the nail heads are printed on the bottom of the decal film, not on the top. If you don't wait long enough after wetting the decal and before applying them, the nail heads just come off the decal film when you move the decal off the backing paper, so you have missing or out of place nail heads. This was the most frustrating part of using this product.
The nail heads make a visually interesting detail, but they should be a different color, other than all black. On close examination of Kolon Mayerhofer's Albatros D.III, it looks like the nail pattern is a brass screw followed by 2 steel nails, then another brass screw, and two steel nails, and so on. One positive thing is that the heads are a round shape and consistent in size and spacing, and the decal film is very thin. I used decal softening fluid only in the most curved areas.
If anyone else uses this product, it would be interesting to know what their experience is. I'm not sure why they didn't just produce this product like any other decal - printed on top of the film with a fixing layer on top.
So, that's my experience. I hope this information is of help to others. I am not recommending to not use this product, just that it has some unusual aspects to it.