I had a Corporal Trading composite stock added to my cz .416 but before that I fired 8 shots and it developed a hairline crack where the bolt handle rests in. My mate had his stock crack from the front of the mag box to the forearm tang screw after 10 shots...............................cz Australia (Winchester) replaced his stock with a great looking bit of wood and he had it bedded straight away and releived around the tang etc. 200 or so shots later and no drama's.

Just get it bedded first up, I have a cz .458 redone to a .458 lott and I had it bedded and 2 extra cross bolts added for and aft the mag box.