Double layer is unnecessary, at least for insects, in my opinion because there are very few times you will be without some insulation underneath you. I didn't find it too help much with a pad either, but most seem to.
You could go wth an unattached bugnet, this would also eliminate the need for a double layer. There are a few different styles of these, up to you to pick which will work best for you.
10' or 11' will be decided based on your height. Most hammocks of either length are around 60" wide. That's starting to change with the newer 72" wide materials.
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