Any harm to putting washers under the crossmember?
 

Is there any harm to putting two washers (about 3/16" total thickness) under the crossmember at each of the 4 bolts? That is the only way to get enough clearance to stop my Stillen CBE from rattling. I've found a couple of posts saying it is a bad idea but I want to be as sure as possible because I'm happy with the Stillen other than this and don't want to replace it if it's OK to just leave the washers there.

I dont see a problem with it.. the 350 guys do it..

Did you try hose clamps on the rubber donut hangers? Very easy to raise the system a smidge with this technique.. Worked great on my car to get that little extra..

This is what I did and still do :)

Thanks for the suggestion but unfortunately I'm no longer able to get under cars and do stuff like that due to a spinal cord injury. That's why I've had to take it to a local muffler shop for this work. I watched the whole thing and made sure they did everything that Stillen said, but on the third trip back it was no further from the crossmember than after the first two tries. One of the guys suggested the washers and I knew other people had done that, so that's what we did. I'm just not real happy with modifying the frame of the car like that. If the washers aren't a good permanent solution, I'm going to buy a different CBE. I like the way the Stillen sounds and don't want anything louder and don't want blue tips with my red car, so it'll probably be a Invidia if I do change it.

On my G sedan, I just took that thing off... the only purpose it serves (at least on my car), is to keep the exhaust from falling off should anything go wrong. There are no performance/structural benefits from that thing.

The one on the Z might actually be different though, being an actual sports car... but if it's flimsy like the one on the G, just take it off and screw the bolts back in to where they were originally.

I used the washers on my 350Z, and I use them on my 370Z. Nothing wrong with them at all.

Wasn't this crossmember-hitting issue solved already on the Stillen exhausts..??

It certainly wasn't on mine. The guy that installed it followed the instructions exactly. I watched the whole time. By the time I got home it was rattling. I took it back and it was only about 1/16" from the crossmember. He loosened it up and pushed it up again. It was about 3/16 from the crossmember when titghtened. A few days later it started rattling again. I called Stillen and they said to loosen the bracket on the cats and all the bolts and do it again. When I got to the shop it was 1/16 from the crossmember again. He did as Stillen instructed and it was 3/16" from the crossmember when everything was tightened, exactly like it had been a week before. We put 2 washers at each bolt as spacers and that seems to have fixed it. Some people have this problem and others don't. I wonder if it is a slight variation in the cars or what.