Since T376845 probably isn't going to be fixed any time soon, it would be great if we could do a quick fix to address the most egregious problem with chart sizing, which is that the (unchangeable) height of charts is ridiculously tall. As @Wellverywell wrote at T376845:

The default size for charts is monstruous, even with width: 800px limit. Ruwiki users are massively complaining about them, calling them ugly and gigantomanic.

This opinion is similar on English Wikipedia and the main reason the Chart extension is getting very little adoption there. Just take a look at the examples on https://www.mediawiki.org/wiki/Extension:Chart. Maybe everyone at the WMF has huge monitors, but for me they take up the entire height of my monitor. Even a modest reduction from the current 607 px to 500 px would be a huge improvement, at least until the more substantial work to address T376845 can be tackled.