I am at my wits end on this one. I am a new user to solidworks so I am unaware of advanced surfacing techniques. I am trying to create a curved surface for the bottom of a skateboard I am designing. I have tried a few different techniques like boundary surfaces and freeforms with no luck. I need something to make the curvature smooth without messing up the edges. Could somebody please guide me towards what techniques I need to use to accomplish this? Thank You.

Attached is an example of what I am trying to accomplish and a few files of my board