2_i 

Thanks for the video. You seem to be screwing on more than I did, when putting the chuck on, and unscrewing less than I, when taking off. The disturbing amount of air coming out from Presta when putting the chuck on is somewhat consistent with my experience. I say disturbing because the air is not supposed to come out at all from the Presta. Of course this is idealized, as usually you touch the stem, but the amounts of air coming out tend to be minute, hardly registered on a gauge. In any case, I think I take less time to put Hirame on a valve and some other chucks too. Lezyne heads take longer, but they can be quite precise once you get a full control of them. So then the only potential attraction of Jaco is in the swapping Schrader and Presta. However that is actually cumbersome, as it is hard to grab firmly the narrow strip on the chuck to accomplish the swap. Moreover, for me the chuck started moving from one position towards another when I was screwing it on. So overall I think I am quite happy having returned it. Even if I learned to use it better, the reason for the unhappiness with the chuck could have just shifted a tad. (This goes back to the question of why looking for anything better than Hirame .) Also, the Birzman troubleshooting video suggests that the experiences may depend on details in the valves.

P.S. I think there is one definite advantage to Jaco, in that it is quite compact in spite of being dual-valve. Some dual-valve chucks can be unsuitable for tight spaces.