I am a huge fan of means-assessed expenses, who often shares commitments with those who are both uncomfortable with that, and yet don’t feel that splitting things equally is fair either (or who simply don’t want to live under a bridge in a cardboard box because one of N people is a grad student or starving artist).
So from that perspective, thanks for the % idea – the math isn’t much harder and it adds to the options if this comes up in future!