A few of thoughts.

1. It is impossible to test a UBI. The fact that the payment is part of a test affects how people respond to it.

2. A few tweaks of the income tax system would recapture the UBI from the wealthy. Make the UBI taxable and then adjust the brackets accordingly. The expense would thus be covered by taxes and a reduction in the many costs of dealing with the impoverished. (Don't forget the multiplier effect; poor people's spending is someone else's taxable income.)

3.The tax system is the best way to do a UBI. Anyone whose income taxes would exceed the UBI would just reduce their withholding. Everyone else would file a tax return and get a refund. The poor would be able to "borrow" the refund from the government interest free, so long as they file a return that claims the credit.

4. UBI should not replace all benefits, just those that are now reduced on account of income. Social Security disability payments, for example, would continue.