Gents:
The 66mm "T", non-counterweighted cranks are OK for a race engine. In fact, they spin up quicker.
For the record: ALL,........ALL 911 cranks are forged;.....they never sold a 911 with a cast crank. These things are quite strong. In 30+ years of racing 911's, I've never seen a broken non-counterweighted 66mm crank.
For street use, they shake a bit more than counterweighted ones and that does affect case life. I would recommend that ALL of these mag cases get shuffle-pinned to reduce fretting on the case half parting lines and extend main bearing life.