You can use depron, but you will need to add supports to parts of the plane. Just feel for what parts are flexing and support them with carbon fiber rods, fiberglass rods or even BBQ skewers can work.
Unfortunately life got in the way and stayed in teh way and I have not created a video or write up on the V3. What pieces are you having a hard time with? Pictures or screen shots would be great.
I'm not quite sure what you mean by center and third section. I may need to pick up some foamboard and just do a live stream building this plane. Or... create new plans that have a traditional wing rather than KFM style lol.
Correct, the top and bottom layers are one piece that fold over the center layer. Peel off the paper from the inside where you make the bend, and be careful to not snap the paper on the outside.
As for changing username, you can request a username change once per year by going to the following link and click on change.