This is my 2nd wing with basic packing foam. It's got a balsa center pod, which I got the idea from, in another thread that had a link to a plane called the Bizz.

the center balsa section is just under 4" wide, with a replaceable foam leading edge, the CG is at 23%, had it at 15% originally, but it was very unstable.

It floats pretty well on a 10 k wind, does even better with stronger winds, being able to perform acrobatics. The wingtips do have Velcro attached winglets.

I used push-rods and buried them in the foam down to the trailing edge.