The LP08 is a PISTOL, not a rifle.. I think your customer had unrealistic expectations about the accuracy. As a pistol is not that bad..
If he should complain about the design of the LP08, he would have to dig up George..
I usually shoot my arty at 50m, on that range im happy if I get within a radius of 15cm. To compare, three of my scoped rifles would go within a radius of 1,5cm at the same range.
..I guess that would make them 10 times more accurate than the LP08
(btw. my groupings with the stock is pretty much the same as without)