I think this seems like a good change but this would need to also be done in Dockerfile-debian.template and Dockerfile-alpine.template, but if it shouldn't be applied to 7/, then we'll need to do something in update.sh to fix them.

Maybe something like this at the end of the for variant in fpm-alpine fpm apache; do loop?

# untested
if [ "$version" = '7' ]; then
	sed -ri \
		-e 's/(opcache.memory_consumption)=256/\1=128/' \
		-e 's/(opcache.max_accelerated_files)=20000/\1=4000/' \
		-e '/symfony/Id' \
	"$version/$variant/Dockerfile"
fi

This would probably be easier to implement in the templates themselves now with #190 👀

(No more hacky sed expressions 😅)

I'm going to close for now, but would love to see a new PR that implements this (especially one that links to the appropriate Drupal/Symphony documentation for where this recommendation comes from 👍).