Im new to surfacing, and Im playing around trying to build a smoothly shaped case. I'm trying to loft but it keeps going out of shape between the profiles where I don't think I can add a guide curve. I'd like it to be flat along the back, and the profiles are all converted from one another so their dimensions are consistent, as well as the spline being tangent to the straight line, so I dont understand why it think it needs to curve outwards before it curves inwards.

http://i.imgur.com/ipiKX16.png  As you can see along the red line it begins to curve outwards before the spline.

I understand I may have failed to explain this very well so if you need some clarity please ask

Also, if anyone can direct me to any resources that can give me lessons in surfacing I would appreciate it (if external links are allowed) because I find it quite confusing.