My CVC needed a neck shim. I just couldn't dial out a zing around the 10th-13th frets. Relief is fine, but the saddles resembled the NASA chase cameras for shuttle launches!. I've just shimmed it near the headstock end with a 1mm thick by 5mm wide strip of fairly soft wood, running across the screw holes and reset the saddles to suit. What a difference. Bye-bye zing and zizz!. No nasties up, down or across the neck anywhere now. However, it does leave a gap, albeit a small one. Is it OK to have that gap long term?, is it any worse that the micro-tilt?. I read on the Internet ( so it must be true ) that over time, the neck settles to the gap and renders it unusable. I can't quite see that, given the thickness of the heel. As this has cured the last ill on my CVC, I'm happy for now, but realistically, is there any real risk of long term deformation?