Howdy there.

I'm in Central Texas, and have a tropical hibiscus that I've wintered outdoors before (in the ground) but last year it died back to the ground in a deeper freeze than we typically get around here (Austin) and came back from root.

I cut it down to ground level.

This year I'm not sure what to do because it has 'trunks' the central branches have become woody and are about 2" in diameter causing me to really not want to cut them back. The tips of the outer branches are green, and I anticipate loosing those, since we dip down pretty low at night, but the hibiscus is in a full sun location and we come back up to the mid-upper 60's by day.

The bush is about 2.5 feet tall.

How much should I cut back after it drops the rest of it's leaves?

If it manages to hang on through the next couple months, then it should be an absolute monster next season :-)