As I discussed else where (… switch to new input script?), it is necessary to switch to a new input script, defined by you, when the spuCraft passes through the light gate.
However, if you switch input scripts a half second or so after passing through the light gate, you’ll probably be fine. If you switch just a little too early, you’ll probably be fine too.
Since you do not have to make the switch at a precise time, you can use the manual switch rather than the trigger.