OK, here's a pic of the 2 different baffles.
The one installed is the 3" track day baffle. With this baffle I've also extended the collector section to about 15". From what I've read this longer collector area should work pretty well with the LS1.
The thing I like about this design is I can change the collector length or put in a venturi style collector insert and not affect the look of the side pipe.
The baffle on the ground is the 2.5" street baffle. This one has a cat converter incorporated into the front of it. The OD on the cat body is 4" (add a bit for the welds) and the OD of the outer skin of the side pipe is 4.5" so it slips over the whole thing with a bit of an air gap. I'm also going to try wrapping the cat in some fiberglass exhaust wrap tape to limit the heat transmitted to the outer skin of the pipe
Here's a couple of pics of the billet rear mounts I made for the pipes. These have turned out pretty nice and look like they will work OK too. They are attached to the chassis with rubber mounts. They should let the motor rock around but still support the end of the pipe.
The mount is sandwiched between two steel plates welded to the body of the side pipe.
I've got to get these pipes off to the ceramic coater. I really want to get them back and hear them run.
Cheers