I've shot two. Both of them, and most of the others that I've seen or held have a LOP of 15-15 1/2". Too long for me. This makes a rearward balanced gun even more butt heavy and forces the hands too close together. It's one of those small problems that should be addressed for bullpups to take off IMO. And Kel-Tec might have done just that. From the photos it looks like thier .308 bullpup has a 13-13 1/2" LOP. And they are talking about building an even smaller/lighter gun for the 5.56mm, 7.62x39 and 6.5 Grendel length cartridges.
