Quark 125b post thermal behavior

You might be overgeared if you are thermaling that quickly. I would try some smaller pinions first. Even if you put heatsinks and fans I think you will still overheat with that kind of gearing. In my hyper 7 I run 12/51 on 4s and it is perfect. So you might want to start with lower gears and go up from there if there is no problems.