At the bottom of HW's Stock .pdf (click) you will find some recommendations.
LRP natural timing is rather advanced even at there zero, so using alot of ESC timing at lower RPM seems to add temp in my experience.

I'd test run 7.5fdr with
#9 - 6
#12 - 5
#13 - 4
#14 - 3
#15 - 5
If temps allow move a pinion at a time towards your 6.8fdr.

Or try
#9 -7.
#12 -3.
#13 -5 (maybe 6).
#14 -3.
#15 -5 or 6.
and move pinions.