ive got a DF03 with a slipper and stock gearing. I installed my Mamba Max ESC and the Novak 5.5 and took it out for a spin in some loose gravel. The buggy came back with a Very hot ESC and motor and some serious cogging issues. I think the cogging can be cured with a software update but im pretty sure the heat is related to the 26/82 gearing that is supplied with the kit. It would be great if someone could recommend a ratio that is good for bashing. Ive been relegated to using a 4yr old TZ that barely moves...
Ive read the Novak Sensored motor is one of the few that do not run well with Sensorless ESC's unlike LRP and Orion (I run both of these Sensored and Sensorless). That could still be an issue.
I worked out the internal gear ration of the DF03 to be 3.00:1. That makes your ratio 9.6:1 using the 26/82 combo. The LRP 5.5 has a recommended ratio for 4wd offroad of 13:1 so I reckon your running too high. A 20/82 should give 12.5:1 and 19/82 13.1:1. I suggest going down in your pinion size or also using a bigger spur.
Also the DF03 doesnt have very good air flow over the motor so they will heat up more than other buggies.
I could be wrong of course but I hope this helps.