Melliot,
I would contact Joe T at A & C. Per the manual there should be some type of body mounting vibration material on the frame rails where it comes in contact with the body.
I have over 14k miles on my 2001 build car. The only stress cracks I have are coming from the corners of the side pipe cutout on the pass side.
I believe they were caused by an object thown into the wheel well from running over it.
No other areas.
Was the body a colored gelcoat or was it a painter body.
If it was a painter body then painted, I believe there has to be some body prep before painting.
If it was a colored gelcoat are the cracks down to the fiberglass? Was the body clearcoated? There are alot of issues to be aware of.
But there should be some type of vibration barrier between the frame and the body.
Like I first said call Joe T at A & C.. Their website is
www.acautos.com.
Jim