I recently purchased an alu-frame 800 FT 16j, (used but had been bought new last June by the previous owner who barely used it and has now given up shooting). I knew about the POI shift reputation but the price was too good to pass on. I did encounter a shift, normally 1/2 mildot down, 1/4 mil dot left. So in an effort to cure it I placed the sight in a BKL 354 cantilever mount mounted on the front breech block only, but it didn't work. (The previous owner had had the sight mounted on the rear block but had not used the rifle enough times to notice anything). I then removed the weight from the front of the barrel, lo and behold the POI immediately returned to where it should be. I put the weight back on and the POI shifted again. By moving the weight forwards and backwards I found the POI would shift again to different places. Took it off and the POI corrected again. I repeated this process five times with the same results. I have now left it off. It now appears to be behaving itself. I somewhat puzzled by this to say the least as the weight seems to have no effect on the rifle other than balance that I can see. Anyone know why this would give the effect it did? And what other causes are there to watch out for? I was also considering having a CF shroud fitted to replace the stainless steel one and allow the barrel to float. Is the shroud epoxied on like the old Dommies? Any advice or info appreciated.