Am having fin converting a cheap $225 Chinese-made cello (solid wood amazingly - just plain looking) to a mini bass. Am waiting for the tuning pins a friend sent to arrive for the final iteration. The holes will be re-reamed, then the pegs fitted. Am using medium weight smooth wound Electric Bass Guitar strings with the bottom string either a .105 or .125 depending upon the sound and tension. A little bit of increasing the notches in the bridge and nut as necessary for the increased string diameters. Same for the tailpiece and pins where the strings anchor. It may not be as loud as a 5/8 or 3/4 bass but that is what amplification is for. Given my arthritic knees I am happy to play it sitting down - though I plan to put a longer and more robust end pin in this eventually. The nicest thing about it is its light weight and portability.
The electric guitar strings have about the same tension as cello strings so I am told. It will be tunes to the standard tuning in 4ths with the top being a G. Already in its preliminary set up I am having a blast with it.