Re: Any ideas as to why it's so rare to see an 8-string electric.
Mmm, not rare for at all, I see three or so 8 string electrics every time I walk into my music room.
I also have two others out on loan to friends at the moment.
I do prefer the feel of double course, and although I can find way around a 4string, it does feel more like a soprano guitar than a mandolin.
Hereby & forthwith, any instrument with an odd number of strings shall be considered broken. With regard to mix levels, usually the best approach is treating the mandolin the same as a cowbell.