Banjo schematics, sizes etc. (need assistance)

Hello everyone. Greetings form Poland…
For starters i need to mention that i have never played banjo, i haven't touch it, not even saw on with own eyes (not mentioning photos, videos etc. that is). I’m a straight harmonica player with no greater skill nor talent whatsoever… But banjo was always my dream instrument. Unfortunately its incredibly difficult to find someone who could teach banjo playing in my country, its also very hard, and unbelievably expensive to get a 5-string, left-handed banjo out here…
That's why i decided to craft my very own piece from scratch… And here comes the hard part.
I need some kind of schematics, mainly sizes of various parts, especially neck length, wight (separate for the 5-string section, and higher 4 string section, distances between threads, diameter of the rim etc.)
I would be incredibly grateful for any kind of assistance you all could have given me.
(Sorry for all grammar errors I've made, I'm actually much better player than a scholar ;) )

Regards, Lucas