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Search "Hart Razor Bevel" angle on here while you are at it :)

See assumptions can mess with you, as you are going to learn from the search early Hart razors had a bevel angle that was more in...

http://straightrazorpalace.com/advanced-honing-topics/82698-honing-without-tape-testing-theories.html

Since you say the edge is holding after you apply the tape then that leads the answer to Geometry, however that might not be the entire answer..

If you have exceptional steel it can perhaps hold...