The hammock pictured on the home page of this site was made with these instructions, and uses the sewn on bugnet design shown in the bug net DIY guides.
Double layer hammocks have at least four advantages over single layer hammocks -
1) they are stronger, so they hold more weight,
2) if one layer suffers some damage, it is less likely to cause a failure as a single layer hammock,
3) they hold a pad in place between the layers,
4) and they have a great track record of stopping mosquitoes from getting you from underneath.
This design is optimized so you can slip a closed-cell foam pad (or inflatable) between the layers for an inexpensive bottom insulation option. Having a pad between the layers helps keeps it in place, where a pad simply placed on top of your hammock is rather tricky - it tends not to like to stay where you want it and, while fun for others to watch, can be rather frustrating for you. If you will be using an underquilt anyway, a single layer hammock may be a better option if weight savings is a key factor for you.
Note: For a single layer hammock, just cut the fabric to size, hem the edges, sew your end channel, gather the end, and add your suspension. Easy peasy!