Exhaust system rattles

[Gadzby at aol.com (Gadzby@aol.com)]

After a new TT cat/downpipe was installed on my 16V last week, the 
muffler/exhaust system has been rattling against the underside of the car from time to 
time.  Here are the symptoms:

1)  Metal-on-metal clanking/rattling sound eminates from behind and below the 
driver
2)  Only happens after 10-15 minute warm-up
3)  Happens mostly when coasting down a sloped hill, foot off the gas, where 
the engine is acting as a brake to keep the car from accelerating

Here's one theory: it looks to my inexperience eye like the muffler is 
hanging about 1/2 to 1" too far back (when the car is stopped, all three 4" long 
rubber muffler hangers are not vertical, but are being pushed toward the rear).  
Hence the resonator input line may need to be pushed further onto the end of 
the catalytic converter output line.

So my questions are: on an OEM Scirocco are the hangers normally vertical, 
and does the exhaust system primarily move front to back, or up and down when 
the engine rotates?  If it moves 1/2" or more back in the "foot off the gas" 
condition, maybe that's my problem.

TIA,
Grant

P.S. I took tome jpegs of my hangers, if anyone is curious to compare.