Hi Gareth:
Loft-Loose option is a sort of "organic" tool...Andrei Samardac did a lot of examples about
You can't rule this tool but just have an approximate control on it
It's hard to get a good rounded transition between to different shapes,even if using same splines with same number of points
My raw attempt is to loft using first and last set of curves leaving out middle complex part
now delete middle curves and draw two lines (red) to cut the edges just in the complex area,so do a Blend G2-0,25 value




now use blend to connect the rest with same value,then join all surfaces
if you want to check joining process is ok activate-show naked edges-and use Dinos Lightning Plug-in to check reflections on surface




I attached the file if you want to have a look,it's just an alternative way,better to follow Michael's suggestions... ;)

M