As I said I've seen plenty of Hummels with numbers, and yes plenty without them, but only a single one with a visible letter, which was followed by a number.
I chose to use a number since the side looks frankly a bit empty and dull without them, and since there clearly are several historical presedences for it that's what I did since it looks better IMO.

No, I don't mind the number, it's just a historical reference for you, nothing more

I've seen several Hummels online, models, paint schemes for models, paintings and photos of surviving examples, that all had numbers similar to the one I put on it.
If you don't like it feel free to remove it.

The historical shoal humel was not numbered, but instead its numbering was in letters from a to f.