Any looseness at all, with the forend off, is a problem to me, and should be dealt with, IMO. Once looseness is observed, I believe the problem is magnified quickly by continuing to shoot a gun in such condition. I have two guns right now that I have dealt with by shimming the hook. One is a BSS which I use a lot for clays in S X S competition and also for duck hunting with factory 1 1/4 oz. loads. By the time I noticed the BSS was loose it would "accept" a .003" shim and still close, albeit very snugly. The Hollis side lock has been loose for much longer and has never seen anything over 7/8 oz. loads in my keeping, but also accepted the .003" shim with the same resulting snugness.
I will probably have the BSS welded and fixed properly eventually, as it gets used a lot. I'm really just curious as to how long the HVAC tape aluminum shim will last before having it done, and have not decided on a 'smith to do the work anyway. It remains to be seen what I do with the Hollis, a 2 1/2" chambered gun that gets used very, very little. But, one thing is for certain ..........neither will ever be shot again without being tightened, by shim or by proper repair.
SRH