The nano that I use is very good lag wise, good enough for focus. I should point out that I personally use an Axis1 for focus. I use a nano with a nano motor (powered by dtap 14v) for iris, and the same handset on a different channel with a nucleus M motor for zoom (or focus if required). On the last job, my B puller used my nano system for focus on a movi pro, using Cooke S4s, nucleus M motor for focus, nano motor for iris. Worked perfectly. We even put a register pin in the handwheel, and made up pre marked focus discs which made life a lot easier. (But you do need to power the nano motor from dtap).