I was looking at things, had imagined that the plenum would attach to the dash support and then the dashboard slip over that. Tried that with everything loose and was having fit problems (dash would not go over plenum and fit below spider). All could be solved if the spider was off and then dash installed, but then makes getting it out near impossible. I then read that the plenum should be bonded to the dash and installed as one piece. (RCR GT40). Did some searched and didn't find much on this. So question has anyone done this? Thoughts and advice? It looks like there should be about a 1/2 inch bracing put at the ends of the plenum (near the outside of the dash) to keep pressure down on it and make it seal. Anyone have advice or help?