Ok, cool!
As you mentioned, the Arduino UNO is not capable of high framerates. We built a huge installation with 8 arduino ethernets (which ist actually an arduino uno with ethernet on board) about a year ago, so we do not want to buy new epensive arduino megas and ethernet shields.
I will test the version you send this weekend and let you know the results. Thanks for your help so far
By the way: Artnet BROADCAST never worked for us, even not in MM 1.5.