I'm impressed by all of it, but the bellhousing is the best. I once helped build a custom bellhousing out of a piece of 14" sch80 steel pipe and two pieces of 1/2" steel plate, and getting proper alignment and depth was a LOT of finicky measurement and layout work, and using constant diameter pipe instead of the nice curved-side bowl shape made us do a small version of your tunnel work, but it worked out in the end. Pilot bearing fitting gave us some grief, too.

The first time you get that beast off the ground, fly it over here and we can play. I wonder if 300hp and a fast shifting a/t will keep up with 345hp and a two stroke shifting m/t???? At least I'll have more valves....