Why no single-stack? Well, to make a single stack one has to have a narrower slide than the P11. That means you either have to have a MUCH stronger recoil spring, longer slide, or taller slide. You end up with a funky looking pistol that is only 4.5mm narrower at best. So, what's the point? If you can build it to hold 10 rounds, why not? I think that some people expect way too much out of the laws of physics. You want a gun the size of the P3AT with the power of a 500 S&W that kicks like a 22. There are natural laws that we must at least try to follow here, people.
Oh, so how did Kahr do it? Look at what Kahr really did. Their PM9 is the same weight and .1" narrower, but carries 4 less rounds! They did make the gun narrower, yes and they do have innovations. One is the offset link. That's really innovative and good. So, if you want a single-stack KelTec, buy a Kahr!