Replying to Box/Rail designs for summer with Pictures/Drawings

My friend wanted me to post this here...maybe it will give some of you some inspiration. Last summer we built a 12 foot box in like 4 hours, and it worked perfectly. So this year, we're upping the ante and building a 6 foot extension for the 12 foot box since it seemed too short, either a 16 or 18 foot flat bar rail, and last but not least we're going to try our hands at a 17 foot Flat Down Flat box. And just to make this thread a little more useful.... Here's the only picture I have on hand of the original box, with my friend hitting it, photographed by the lovely Mrs. Circe: And here's a concept/sketch for the Flat Down Flat box. I know the down looks too short but there were some reasons. 1. The longer the down, the taller the first Flat would have too be, and our drop in isn't that big. 2. We wanted to make the down small enough to gap it easily and for switch-ups and stuff. Feel free to insult my less than impressively straight lines, and probably incorrect calculations for the angles on the FDF.