here the link to download the Beta test of the network play of Tennis Elbow 2006 (that will be available as a free upgrade to all TE2005 users) :
So far, it works perfectly on local network, without any loss of synchronization.
Thanks to let me know if you encounter any problem.
I set up a chat to ease the research of other players : http://chat.managames.com (it works in PHP, so it's a bit slow, but it should be alright for now as long as there are not too much people on it )
Once connected, the game looks your ping, and then try to find the best lag setting.
I'm not sure if it works good or not, but the basic idea is to set the lag to half of the usual maximal ping, or a bit more.
Example: you never or almost never have more than 60 ms of ping, so you should set the lag on 33 ms (there are steps, you cannot set it with a granularity of 1 millisecond).
Only the host sets the lag, then it's sent to the 2nd player before to start the game.
PS: don't try the World Tour, it misses some players to work correctly !