I know Bela received some reports about the EC2 environment sometimes dropping datagrams > 32k, so I wanted to make the default safer.

The default udp stack also had a frag_size of 8k and a max_bundle_size of 64k, which didn't really make sense. I would have preferred to make them exactly the same, but JGroups doesn't allow setting frag_size == max_bundle_size, so I settled for 30k/31k.