(2nd August 2006) The first image below shows the firewall from the front , with the recess on the floor. Image 2 shows, from the cabin side, the recess installed temporarily, with the grey floor cover with fluted slots for cabin heat delivery. Note that this cover attaches to the recess with platenuts and screws. Image 3 shows these platenuts installed. Image 4 shows what happens when you drill a hole in your finger - I must be more careful! I was holding a reinforcing plate on one side and drilling blind from the other - stupid. Image 5 shows the positions of four key holes which need to be cut in the forewall - one large 2" hole for heated cabin air, and three smaller holes for throttle, mixture and carb heat cables.I measured carefully rom teh drawing, and used a 1/8" drill to make pilot holes in the proper locations. I then used a 2" holsay to cut the cabin heat hole, and my nifty hole-cutters to make the other holes. Image 6 shows the result. The next job is to make a small plate to reinforce the firewall where metal fittings need to be attache to carry brake fluid through from one side to the other. Image 7 shows this plate clecoed in place at the FRONT. Eventually it goes in the back. I match-drilled all 3/32" rivet holes before drilling two 1/8" pilot holes where the fittings will locate.