2005 4.6l EB Replacing Exhaust donut, how tight?

[WaterBrat]

The engind sound changed and I heard some rattleing under the drivers side. Think there is a slight exhaust leak. Ordered donut and new sprong bolts for flange between cat and muffler. In putting back together, do the flanges mate, or how close/tight do I make it. The new bolts are NOT threaded the whole length. I have already freed the bolts using the ATF-Acetone mix.
Thanks in advance for guidance

 

[WaterBrat]

Once I got underneath to do the job it was pretty obvious. Flanges mate pretty close. I had to cut one of thye bolts off. Job done and exhaust quite again.