The thing about the big upright bass is that mine isn't the highest quality bass and I find it quite difficult to play. With D6 tuning, you can do a lot of I-IV-V chords in the key of D by playing all open strings. However, since I made the switch to C6 tuning, the open strings aren't a viable option anymore. In the ukuleleyes article I link to above, the authour Steve Boisen mentions the Kala U-bass as another alternative for adding a bass to a ukulele group or classroom.
I found one on Kijiji. Because of various circumstances, I had to buy it sight-unseen. I discovered later that It is a little worse for wear. This particular one has decent intonation on the G and D string but it is out by pretty much out a half-step for the A and E strings. I was told by the Gold Tone company that new strings should help. The other problem is that the fret edges are sharp.
I am a little sad because after the added expense to fix the frets and strings, it will no longer be that much cheaper than new. But on the bright side, we do learn some things here. First, there is something about the strings. I don't know exactly what it is yet, but the rubber strings seem to require some added maintenance, or maybe these ones were just really abused. The other thing has to do with the fret edges which are sharp. This is likely because of a lack of humidification for this instrument. Even with dry air that probably shouldn't be happening but it seems that it is simply the reality of new cheaply manufactured instruments where the wood is not dried out properly before the building process.
Anyway, I am still excited about the Gold Tone bass even with some of the problems I noted. I look forward to trying it out with some ukulele classes after the busy Winter Concert season is over. I also look forward to trying it out with the ukulele circles I run. I will let you know how it works out.