I finally managed to complete another "bi-species" bowl without going through the bottom of the inner bowl. This one is padauk and cherry, which will probably be a really bad wood combination once they both age. The bowl is 4 3/4" across the flats of the octagon. The inner bowl remains a suprise until the lid is removed.
The outer bowl is turned basically to completion except the interior is not sanded. The inner bowl is rough formed on the outside and then chalk line chalk is sprinkled inside the outer bowl and I start to test fit. I keep removing the chalk marks that show where the two bowls rub and repeating the test fit until I get it as close to a perfect nesting fit as I can. I then epoxy the two together and once the glue has dried I re-mount using the same tenon or recess as I used to originally turn the outer bowl in order to hollow the inside of the inner bowl.
I had screwed up two attempts since my original one last summer so I was pretty cautious on this one to ensure I wouldn't go through the inner bowl anywhere, so the walls are a bit on the thick side. The side walls and bottom centre are about 1/4" thick and the "foot" area where it rests on a table is about 3/8".