9mm is a really temparmental cartridge regarding seating depth and pressures. In my Speer manual they used an established SAMMI load that was producing an estimated 28,000 cup (psi now). But when they deliberately seated the bullet .030" deeper than SAMMI recomended, pressures went from 28,000 to 62,000 psi. If not for the fact that this was performed in a test barrel, I'm fairly certain that would have resulted in some sort of catrastrophic failure, probably a ruptured case or possibly KB in a porrly made firearm. I've got a pretty nice amount of data for the 9mm because I load for it also. Tell me what bullet brand, type, and or part number you are using, and I'll see what I can find to substantiate a safe COL for that Kel Tec.
Hornady 115 gr. XTP showing a COL of 1.075", the FMJ is at 1.100".
Sierra is @ 1.050" for JHP & 1.100 for FMJ
Speer is @ 1.125" for Gold Dot and JHP. The TMJ is @ 1.135"
My advice would be to load a few with 4.3 grs. which is Winchester's listed minimum, and seat them to the longest COL that will chamber consistently and give them a try. I seriously doubt you'll have a pressure problem given the fact that the COL is in the ball park at 1.070" for some of the bullets listed. If all goes well at 1.070" with the 4.3 grs. of 231 maybe try giving yourself a small margin by going to 1.065" to avoid any chambering issues due to olgive inconsistences. Then if the 1.065" goes well which it should, you can begin working back up to your powder charge of 4.5 grs..
Sound good to you?