Hi Goliath, I got one of those Nomad hammocks in the BCUK group buy as well. (about $40 delivered )
I lie on the diagonal and don't have as much problem as you with floppy sides. I move between lying on my back diagonally and on my side foetal (again diagonally). On my side I have 'flop' along my legs which I just see as a bit of extra insulation.
I've also added a ridge line to set a consistent sag. Originally I used some carabiners to attach this but now I just have a bowline at each end and slip the bit of black rope that came with the hammock originally.
To the black rope I have also larksheaded some rings so I can use straps to attach the hammock.
The way you have set yours up seems similar to the way some people from BCUK set there hammocks up so if It keeps you of the ground more power to you.
Thanks for pointing out the obvious that I can whip the hammock as I want to. I'll have a go at roll whipping mine like I did with my 'bigheadessy' since that way has been the kindedst to my knees.