Hi. I just spent some more time thinking about integrity checking and discovered this: lzip can be easily tricked into reporting truncated file as correct!
Let's assume I created .lz file by concatenation of two .lz files. Then I sent this file over internet and file got truncated. If the file got truncated exactly between these two concatenated parts, then truncation will not be detected by lzip!!! This is format's design bug. We cannot do much on it. At least please document it in "man lzip"