I print with a .8 Nozzle and when I changed up after changing it in the printer settings I had to go close the program and go back in. But that was quite a few versions ago. Also you know that slicing for a .8 nozzle a .6 layer height does not make much sense. I have never printed with carbon fiber but I assume the Nylon and pla around it does not melt any faster than regular Nylon or PLA or whatever. Now The fastest I got PLA flow on a V6 and still get a decent print is about 13 mm3/sec For Nylons its 8 t0 10. So if you use PLA and you are running it hot so you can get the 13mm3/sec that means printing MH PLA at 225 (slower and you drop to 11 mm3/sec) then your fastest print speed at .6 layer height will be about 26mm/sec (.8 * .6 is roughly .5 and 13/ .5 is 26). that means at .4 its about 40mm/sec. Furthermore tests have shown that the best layer adhesion with pretty much any material is between 25 and 50 % nozzle diameter so for a .8 its between .2 and .4. So printing at .6 makes no sense at all you get a crappier print with poor layer adhesion and even worse if you don't dial down the speed to above mentioned range I did a video on that https://www.youtube.com/watch?v=kugqYO-Jang&t=54s I Got a pulse C232 too