They sent a replacement...
CTC said the gap is normal on this grip. A Customer Service Supervisor said he has the same gap on his personal gun. He offered to exchange the LG-405 for a LG-305 but could not guarantee that it would be any better.
I think CTC's Customer Service has been friendly and easy to deal with. However, I must say I am disappointed with CTC, overall, because they think this is an acceptable $250 piece of plastic. I don't feel I got what I paid for.
They really need to set their customer's expectations by including 360 degree images of all of their grips on their website so buyers know what to expect.
Crimson Trace LG-405 - S&W J-Frame