Testing search engine parameter improvements is good.
If "success" is principally measured by whether users save-to-tree, I hope that some factor such as subtracting 50% will be applied.
A great many newbies have little idea of what constitutes a "match." One of the recent examples I have noted is frequent saving of a US Census item for southwestern PA to a tree family who never left North Carolina according to the myriad copied trees. This item's relevance is suggested by the hints system because one treebie did the initial tree save, and the hints system may be giving it greater relevance (to wrong family, mind) weighting as others followed suit.