I don't think you can do small scale experiments, unless you do it using an entire small country. The idea is that you raise taxes too, and naturally you'll have winners and losers. I don't think the losers (wealthier people) will tolerate being forced into the program while others are left out of it. If you let people choose, then only the winners (poorer people) will choose to participate, which will deeply distort the results.

If you can do such an experiment (by, for example, instituting BI in a small country) then there are certainly outcomes that would indicate BI isn't feasible. The big questions are whether people in a BI scheme will continue to work, and whether the higher taxes needed to pay for it will kill the economy. If everybody quits their jobs and the taxes strangle the economy then that indicates BI isn't feasible. If everybody keeps working and the economy proceeds as usual then that indicates it is.

I don't think Social Security is a useful example precisely because it's aimed at retirees. You don't get much useful information about people's willingness to continue working when you target it at people who have retired. The tax rates needed to support it also look artificially low because the SS tax base is much younger than the SS recipients, and population growth means the former group is disproportionately large. Finally, it doesn't really look much like a BI scheme, because what you get out of SS is based on what you paid in, it's not at all universal.