Get hold of an octave mandolin. it has a deeper thrummy tone, yet the stringing is identical. Mine is a Trinity College, and has a 20 /12 scale--thus,most mandolin fingerings are possible.
So in a sense, you *are* practicing mando, but with a fuller sound.

And it's an excuse to get yet another acquisition!

Folk of the Wood and Elderly both carry Trinity College 8mandos, for about 400 eaglebucks.

Rich