The BugSock does fit over the UQ.
The length is normally determined by adding 4-5" to the length of your ridgeline. This gives you enough length to cover the gathered ends of the hammock, yet not be too baggy.
The depth is normally 53", but I have made them down to 48" for folks that don't need or want the add'l room and want to save a little weight.
An important thing to keep in mind is that when talking socks, or I guess any nets for that matter. The BugSock depth also affects the width when you are in the hammock. If you increase the sag and lay further asym, you are also pulling up the sock on the bottom.
Hope that helps.