running the solid rear engine cover will definitely allow much cleaner air to get to that rear wing and as such allow less AOA.
On mine and Jamies Time Attack cars we both went for solid ones verses the motorsport vented versions that are avaliable for better aero and both have the same dual element wing.
Jamie has 600bhp+ and runs his main element at minus 2 degrees I believe with 1600lb springs on the rear so it makes some decent downforce, im sure you know this but because the air will be attached to the engine cover it will interact with the wing at a different angle, so you might set it at 0 degrees but infact the wing is getting air at 5-10 degrees.
Dallasreed, those wing uprights dont look strong enough for what your doing with it, that wing at 150mph will probably be making circa 400kg of downforce, thats 4 very large guys sitting on it, would you be confident to do that, ive driven without my wing at 80mph and even in a straight line it felt scary, i wouldnt want it to fail at high speed on track, ive had that and been thrown into a wall at 90mph so wouldnt want i to happen to anyone else.
Mine are made from 12mm pure carbon fibre which i will be cutting some holes out for weight reduction but even so, they are 700mm x 220mm x 12mm an weigh 1.2kg each
i would suggest you thicken up your supports or at least cross brace them, i use carbon rod for that.
This is at 80mph with my wing, on 700/900 setup for testing, my diffuser is normally 80mm from the ground when static
Also Phil shouldnt have any issues with temps, that rear wing will create a low pressure zone behind the car and help pull the air out, aswell as the natural pressure differential between in and outside of the clam, ive got a red hot turbo 4inches from the back of my head and you can see the exhaust popping out of the side of the rear clam and dont have any temperature issues in there.