I don't think you can swing differently to increase it. The time the ball is actually on the strings is measured in only a few (4-7?) milliseconds, so there isn't much room either way.
Lowering your tension and playing with a more flexible racquet can increase what a lot of players call pocketing or cradling, but if the ball actually stays longer on the strings by any measurably significant degree is hard to say. The feedback at contact for the player is probably percieved to change quite a bit, but the actual length of contact is probably not.
This is my understanding of it, however others who are more informed than me will probably post.
EDIT: by the way, how are you liking the yonex? what were you playing before? I am playing it at around that tension right now.
winter makes it hard to practice serving. off again on again til spring....sigh