Just from my experiance, the Leleupi's are to aggresive for the Labs. I had a pair around 3.5'' and the male would chase and attack the largest fish in my tank to no end. And any time I had them they were the most aggresive in the tank. Just my 2 cents.
From my experience, I had a leleupi and a brichardi in with a Lab, and when they were
small both the leleupi and the brichardi dominated the Lab. But as the Lab grew he tested
their teritorial boundaries more and more until he eventually dominated both the leleupi
and the brichardi to the point of bullying them constantly. I eventually had to return the
Lab to the LFS. I tried this combination twice with the same result.