The Get Some fuselage was built out of 4mm Coro.   See the build tutorial here.  I

I would change the Coro fuse so that the seam ends up on the bottom or the side of the fuse verse the top.  Putting the seam on the top made it difficult to get the wing and the tail feathers to line up and I had to shim the horizontal stabilizer to get it to line up properly.

How I find where the fold lines will go depend entirely on the type of gutter pipe that I will be using. I take a piece of scrap 4mm Coro about 3 inches in width and at least 12 inches in length.  I lay one of the formers on the Coro to determine which flute is the fold line.  I then take my aileron tool and cut the flute out.  I fold the Coro up the side and repeat until I have all four sides done.  This becomes my template.

I then lay the template so that I can use it to line up the flutes (count the flutes) with the fuse blank and the template.  Keep the template because you can use it for all of your Coro fuses.

* The PVC Formers are made from American Gutter Pipe but Canadian will work just fine too.
** I don't use wing dowels, I use Wire Wing Hold Downs.  See here for more info.