Reupping my assertion that kernel network protocol stacks are painfully obsolete in a world of containers, namespaces, and virtual machines. Default parameters are trying to balance competing interests, none of which will be relevant to your use case. Userspace protocol stacks are more aligned with the end-to-end principle. QUIC is a convenient compromise that moves most of the complexity up into the application while still benefitting from the kernel UDP stack with relatively fewer knobs.