Just wanted to report in ...
After two weeks with no DaVinci syrup and three of total compliance, I've lost the same couple of pounds I would have lost otherwise. And the entire loss was a few days after my last "off-plan meal," which is what always happens.
I think my next test will be adding a supplement every day for the next week to see if THAT makes a difference. If not, I'm going back to my off-plan eating every few weeks, since that seems to work best.