RE: RB C5 Engine - Starting Advice for New-to-Nitro Guy
If it's already fully broken in, don't try to make it any colder. I would run the engine from 200-220 or so and mainly tune by sound.
RB motors like to be a little fat on the bottom and scream up top. They are a wicked motor and all I run in my 1/8 scales for the past 3 years.