The aero cap held up pretty well...until I encountered some heavy winds just South of Dallas. The hatch main supports were bowing up pretty badly...so I had to pull off the road and tape the entire hatch down just in case the main hatch exploded. Made it home without any incidents!
Now before I take this version apart and start working on my next version...I'm putting the 2 extra sheets of Coroplast back on top of the hatch to see if it will stabilize the bowing and flexing I was seeing as I was driving.
You can see the bowing here...this was at 65mph and about a 30mph crosswind...
