I have to disagree with your logic to some extent. I didn't do the math, but let us take it as given that I have enough voting power to upvote a proposal past the return level. That doesn't prevent any number of voters from then voting up the return proposal afterwards, effectively stopping the proposal I voted for.

In my opinion, using my voting power as the metric for how much the return proposal level is set at isn't a great idea, since a lot of people just can't be bothered to vote and it takes a lot of voting power to get any proposal funded. In fact, I dropped my voting for the return proposal in order to make it easier for proposals to get funded without my vote, leaving me free to only vote for proposals I really strongly want to support.