Hi ugotaccpaced,

I had quick look at this and I've used the method Michael mentions here http://moi3d.com/forum/index.php?webtag=MOI&msg=4059.5
I didn't go for accuracy, I just wanted to show the method. The blend tool is a nice tool to use for finer adjustment of the look of the blend in real time.
I used the picture links you posted to roughly get the 'bulge' shape in the centre.

I've attached the the .3dm file and in it you'll find the steps taken, if you have any questions about the stages let us know.



Cheers