The VOX is always active. As long as you just use SSB, it's not necessary to do anything with the PTT.
However, at CW speeds higher than 15 WPM or so, my setup tends to "eat" the first dot (no dashes), i.e. either the PA's or the transverter's VOX doesn't react fast enough. If you plan to use CW more than occasionally, I'd recommend to wire the PTT.