Consider the Ultegra BB instead. Dura Ace uses slightly different bearings that arent sealed as well. So you get less drag, but at the cost of some durability.
The thread together BBs can be great, but you need to have a good fit and I personally think they are worth it only if the bearings are replaceable a few times. From the reviews on this site, it looks like that can be done with the ZTTO, but also that the bearings themselves are not good. Given that, I would start with something like a wheels mfg BB that is known to be well made and uses good bearings to start if you felt like you needed a thread together.