If I remember correctly, my Vader model uses 3 dragon scales in an arc. Their intersections are masked by the black color. I don't remember having any problems with collision with arms and legs. Make sure you're attaching to the backside, and makes sure you angle the prop out a bit away from the character to give the body room to move during the various animations.
In regards to attachments and glue... I've done many things and learned a few things. Generally I would say do not glue, just attach. The reason for that being that gluing can cause nasty collision problems if you forget to turn collision off on the props before you glue them. That's easy to do, especially if you're gluing a lot of props. Some exceptions to that: if you have a massively complex character. See my Master Chief as reference. The attach limit is 60. Sounds like a lot, but if you're working with a lot of detail, you can definitely go over. Second instance would be if you have a particularly complicated set of attachments. Master Chief again as an example has a helmet of something like 20 props and 2 characters, which I glued first to make placing easier. Again, though, you have to make sure that collision is turned off on each and every one of those props before gluing, and that you turn it off on the glued object. My Darth Vader gave me problems because I missed a couple. On death, he would kind of float above the terrain. Turned out collision was still on on one of the dragon scales that made up the cape. Last instance is if you have a group of props that need to be arranged together in a very specific way. (see Vader's cape) That's nearly impossible with the character moving around during the stupid idle animation like they do. So pre-arrange them and glue, then attach.
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