B looks like 13, specially on the light weight.
D looks like D

Thanks Pablo.

Back on thinking.

I think it looks like a B, but it’s very much dependent on the context.

This is one old sketch done very quickly then, so there are a lot irregularities in overall layout and whole concept.

A couple of people told me that /B/ and /D/ would look very strange and not enough recognizable as those letters. So that started bugging me more and more.

I think it’s the right-pointing lower terminal (also seen in b) which appears problematic.

What Frode said.
Have you tried having the bottom-left corner of those two characters just as a single curve? (ie, not separate strokes; keeping that characteristic curl at the foot, but then running straight on into the bowl?)