I have done breadboard ends on 3/4" thick material before and I have always used a 1/4" tongue, 1:1:1. I have never made a breadboard end on anything thicker before.
The big 'ash table I am working on is about 3' wide 6' long, 1-3/4" thick. I was wondering what ratio I should use?
Here is what I was thinking,
A 6" wide breadboard end, 1" tongue thickness, 3" deep.
That would leave 3/8" of breadboard top and bottom and 3" of solid material behind it.
How does that sound?