http://www.roundtableplatforms.com/images/Add_Pic_1.jpg
a piece of marine ply at 900mm wide x 2400mm long would be around $120. i will download some templates and cost it up. as long as you get the angles right for the 70 to 80 minute period, this version should be ok to mass produce.
http://www.equatorialplatforms.com/alumplt.jpg
again, it is the angles that need to be right, but the look doos not have to be pretty. i will cost out as well.