I have maxed out G_MAX_SEGEMENTSDRAWN to where it is just able to keep up; after the Chunk32 update, SM has to render up to about eight times the number of blocks. This may not be noticeable in a mostly empty sector with just one ship, but it can make a huge difference if there is a lot to render, like in an asteroid belt, or on a planet.
After reducing G_MAX_SEGEMENTSDRAWN to about a third of where I had it before the update (didn't need to go all the way down to an eighth), everything is running smooth again.
Experiment with that, set it low and work your way up until it starts to break down (give the game a bit of time to catch up between changes), then revert back to the last usable value.