I run .8 mod, 32P and 48P gears depending on the setup. I have more gearing option with 48P then with the bigger gears. The 48P handles the 6s1p quite well. I wouldn't try it on 9s1p though.
Yeah... I ran steel on steel 48p gears on my rustler at one time and the pinion was literally GLOWING red after speed runs with a 6xl on 4s. The motor didn't like the setup too much either... Melted my tranny case. Temp was between 260 and 280 on the motor's final run.