I made the big wing from green foam; you probable can get this foam at any do-it-yourself shop.

I first cut two pieces from the plate (1200mm*240mm) with a hot wire to get the wing shaped. Then I used a sanding machine to do the final shaping, just watch the backside of the wing it may not be to thin (about 7mm) (see the drawing above).
I made the fuselage from three layers of the green foam. The middle layer contains a few holes for the receiver, servo's and the batteries.
The motor hanging is a little different from the drawing, instead of drilling a hole in to the front I've cut the first 80mm from the "romp" then I glued two plates of 1mm plywood to the romp then I screwed a motor-holder against the plates.
I cut the whole romp with a very sharp knife.The hole romp and the big wing can be cut out of one plate 1250mm*800mmThe rudders are made from two layers of Depron Glued together
If you have questions about the plan above mail to question@modelbuilding.myweb.nl