I'm a DB Technologies dealer and own a 16 box T4 rig. I questioned the accuracy of the Composer software from the first time I used it. Specifically, it chose a pick point on the fly bar that didn't angle the rig up far enough to cover the entire balcony. Whoever posted the comment about the angle of the first box being the most critical, hit it on the head. Hello Ease Focus!
Fortunately for me, I regularly work in a local theater (975 seats / 650 floor / 325 balcony) and at times, the rig is in there for up to two weeks at a time. This has given me the opportunity to experiment with different configurations using predictions from both Composer and Ease Focus. The earlier versions of Composer were a mess. The predictions from Ease Focus produced considerably better results, particularly in the balcony. That said, I'm now using V5 of Composer and it's much better in terms of it's accuracy, however, due to my early experiences with Composer, I generally rely on Ease Focus when deploying the rig. I'll have more time to tinker with Composer in the same theater again in about a month. I believe that version 6 is now out, but I'm assuming it's primarily an update to include new Db Tech products. I've not had an opportunity to mix the T4s with T8s or T12s.
With regards to the discontinuation of the T4. My Db Tech rep told me that while they are technically out of production, the factory will build them on request until the end of the year. He also said that he gets a daily update of available B stock units. You should contact the nearest Db Tech rep to see if he can assist you in that regard. I'd like to add more to my inventory before they are no longer available. While they're not the most sophisticated boxes out there, they certainly fit my needs to a tee. The scalability, ease of use and weight (270 lbs for an 8 box hang with fly bar) are hard to argue with. For what it's worth, I've ground stacked them (5 boxes) on an S30N sub per side and with a little massaging gotten surprisingly good results. Of course, I fly them whenever possible, but sometimes it's just not an option.