If you haven't finished, or want to go back... evidently it's wise to idle the car a bit before you tighten the nuts down so it settles correctly into place and doesn't put undo stress on the mounts. Then tighten everything.

I didn't do this when I did my mounts and everything has been running fine for 4k+ miles. Granted the above is to help them from failing early, not immediately. It's best practice but not absolutely critical.

 

Thanks for the reminder.. I did leave the bottom nuts loose as the top of the mount is fixed into two grooves I figured it wouldn't shift much loose or tightened.