You can fork the repo to make changes in setenv.sh e.g.
export JAVA_OPTS="-Dfile.encoding=UTF-8 -server -Xms256m -Xmx4096m -XX:PermSize=256m -XX:MaxPermSize=512m"
I’ve been trying to fix other issues this way e.g. seeing if a different Superset Docker image worked, or trying to configure Zope packing so the VM doesn’t go down in a matter of days when it runs out of disk space.