Yuval,
I strongly recommend that you use some kind of bracket for the tuned silencer; preferably in the middle of it.
If not, you run a strong risk of breaking the header...
Here are two good candidates:
http://www2.towerhobbies.com/cgi-bin...?&I=LXZ667&P=7
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXB864
You can also use the MVVS bracket, but it holds at the end.