. This is because the mtu on ethernet (max transmission unit) is 1496 bytes. By setting the packet size larger, you are forcing fragmentation which means you're more likely to get a correct response (since at half duplex the frags tend to collides and thus don't reach the remote host).
I'd check it against a host you've deliberately set to half duplex, just to make sure it works if you've changed that behaviour.
Glad it proved useful though.