I have the solo axle-backs on my 09 GT with an x-pipe in place of the mid-muffler and I think my situation is very similar to the original poster's although their car is a V6. If I am understanding you correctly, you are suggesting to make an adjustment to the lower clamp section on the j-pipes before the bend starts closest to the actual weld to the exhaust pipe - correct? All I have ever heard of anyone adjusting is the length of the j-pipe at the tail end or the second clamp, which I have tried with little difference in sound. If this is what you are referring to then I believe I would need to go out a little bit so when the car is at normal operating temperature the sound would be closer to what it is now when cold - right? I never knew that stainless steel "stretches" or expands when it gets hot - interesting. I'm just looking for a little bit more refined sound which may not even be possible with my current set-up?
DOH!!! I totally missed that the OP had a V6. Thus, there are no such adjustments on the V6 system. I suggest instead that the OP contact Steve @ SOLO to find out what any troubleshooting the V6 Axleback mufflers may have to see if he can solve his problem.
To Brad: If you're looking for more of a "refined sound" ... you may want to consider the SOLO Resonators. They refine and tune the sound in a way where it takes the 'edge off'. Honestly though, considering you have the axlebacks and an x-pipe, that's one combination that I'm not intimately familar with (I've always played in the catback world) and am not sure.
I guess you could try anything if you have some spare time... just make a mark at the positioning before you change anything, so worst case scenerio, if it makes it worse, you have a place to go back to as a baseline. Feel free to post your detailed results on a new thread too, so others with similar-to-your setup (X-pipe and SOLO Axlebacks) could benefit from you reporting on your testing.
The general rule is that if you make the overall J-pipe length longer, the tone/pitch goes deeper, whereas if you make the overall J-pipe length shorter, the tone/pitch goes lighter. Adjusting these clamps may shift your troublespot to exactly where you need it to be, which is the "warmed up" stainless length.
Hope this helps. Wish I could help more. You're on the right track... now go for it!
And to the OP, sorry for giving you bad advise. You don't have J-pipes, since you have a V6. Thus, you can't adjust the non-existant J-pipes like I described. There goes my reading comprehension. Sorry 'bout that.