I've added a commit that defaults to using a weigher and specifies a maximum weight of 10M. The weigher can be disabled via the registry by removing maximumWeight from the registry setting thus allowing folks to use maximumSize if desired or simply no weigher.
I'm now looking at the backlog of pull requests (sorry about that!). Before I can commit this PR and start addressing your other PRs, can you please submit a contributor agreement?
https://www.python.org/psf/contrib/ specifically the one for Jython
After "merging" another PR, which creates unnecessary history, looks like "declining" is the best approach, so doing that now. We will have this cleaned up shortly, now that we have a better sense of how to manage with respect to bitbucket mirroring vs the actual repo being at hg.python.org