Enharmonic Spellings of Perfect Fourths

Okay . . . still inspired by David Lucas Burge's approach to intervals, let's have a look at Perfect Fourths. Rather than commenting, I'll just asterisk the improbable ones.

Cb - Fb

C - F

C# - F#

Db - Gb

D - G

D# - G#

Eb - Ab

E - A

E# - A#

F - Bb

F# - B

Gb - Cb

G - C

G# - C#

Ab - Db

A - D

A# - D#

Bb - Eb

B - E

* B# - E# (pretty weird!)