Best way to thicken a surface like this?

 From:  Swang (STEVECHINHSUANWANG)
10035.1 
Hello,

I am relatively new to Moi, but it's been a blast trying out the tools. One thing I've been trying to do with little to no success is thickening a "car" like surfaces like the one in the screenshot. The shell function produces undesirable results, and manually patching with loft/network is still given me some naked edges here and there.

Thanks for the help!