I can accept the quality of the top cowl (CF + Coremat + CF) but I was sure the commercial ones must be better. In KY, Greg Cross had one he ended up not using, whcih he said was for a wide deck 360. It was a 3-day 2000 mile round trip but I went up, socialized and brought it home. Then I found it is actually a poor fit - !@#$!. The commercial cowl has the oil door too far forward and the exhaust openings are too tight and incorrectly oriented. The upside is that my Coremat cowl is about 60% of the weight of the commercial product and a lot stiffer. Time to double down on making the lower cowl....

This has proven to be a much bigger task than expected, and perhaps it would have been more direct to flip the plane again. But I persevere. Here's what has proven successful.

I need a tight fit at the firewall/wing root, and then at the trailing edge, particularly around my exhaust eductors.
- Lower profile. I used square cross section aluminum to bridge the NACA duct, providing a shelf/lip for the forward edge pf the lower cowl. The lower cowl needs to wrap around the air intake, alternator and starter, reaching up in front of the ring gear to fit behind the (extended) prop hub. I like having at least a 1.5" gap for the lower engine baffle. I used building sheet foam (purple!) to profile the lower cowl - it ended up looking like a hockey stick. I copied that foam shape onto luan plywood and fixed it in place using 5 minute epoxy. The plywood ends up as a keel for my boat tail lower cowling.
- Wing root match. Using the same wing root profile as used for the upper cowling, I built on the plane a foam block lower cowling. The wing root blocks were held in place with bamboo skewers passing thorugh the wood profiles into the foam . At this point I have gone through a _lot_ of foam insulation sheets, and the cost approaches buying something from Velocity. Moving on...
- I did a rough carving of the foam while in place on the plane. I then (carefully!) supported the cowl while I sliced the foam away form the wing root profiles and firewall. I removed the cowl and reinforced the inside with pour foam and building foam. At the sides I added an additional 3/4" wing profile, copying the wooden ones. The block was then moved to the bench, ending the messiest part of the upside down work. Note that with the interior of the foam core now reinforced with pur foam, this core can no longer fit on the plane.
- Firewall profile. I trimmed a piece of foam board to match the exisiting firewall lip. Fitting it to the foam core I saw that it was not a great fit to the new foam template. !@#$!. After 3x checking the template I used both foam and plaster to get a darn good match. I then re-shaped the cowl to smoothly flow from the correct firewall profile.

[Sidebar: Spray foam was an uncontrolled horror, but it took only 2-3 hours to clean that up. Pour foam is much easier to sand, but expensive and it's hard to predict how it flows before it swells, gells and hardens. I was happy to find a pour foam source even less expensive than my bare bones boat supply distributer - Amazon has some, and they sent me 1/2 g containers of A&B when I had paid for only the quarts. Doing it again I would build on the airplane with blocks of foam, remove and add a thick pour foam layer, shape with rasps, then use plaster to get a smooth surface. Model one side, then cut templates and shape the other.]