Just giving you guys the heads up. This was news to me, but in Brazil 4 and 5 string mandolins are a thing! They call it Guitarra Baiana and you can hear it used extensively in certain styles of Brazilian music. I joined this Facebook group:
https://www.facebook.com/groups/163689640325482/
Lots of Brazilian builders too.

Not to mention there is a whole acoustic mandolin tradition in Brazil (bandolim).
Cool stuff.