My tip got crushed last time I went out. Right now my exaust is cut about 10" - 12" forward of the rear bumper, so it dumps a bit under the car, that far backward isn't a problem though, even when idling at a stop I haven't seen a problem. I don't see myself crushing it there, it's right between the spring and the tank skid, so there's about 2" of stuff underneth it. This may be a good solution for you.
About the muffler and cat..well..there's nothing you can do for those bad boys easily. I'm going to have mine set up with bolt on connections (like the one just forward of the cat) between the pipe that goes over the axle and the muffler, that way if I damage it I can easily drop it out and repair it (I'm also going to have a trail only exaust and a street exaust, the trail only one can be beat to snot and it doesn't matter, you know?)
Sequoia