I believe if probe is 2.5 inchs from piston skirt you should not exceed much more than 1300 for extended pulls. Good rule of thumb is to check plug color and possible wash on piston.
As stated it is the mid range that will most likely be warm.
Have found the same on BB also . Ran a RKT 860 and now the 880 BMP and both seemed to be the same. They need fuel and good fuel.Pto is typically the hotter one. Due note the above temps are correct, but we always found the sweet spot is around 10-1100 degrees. Not sure why but u can feel it pull harder in these temp ranges. Just out groups observations with big bores