I have to ask why?
Seems pointless to me. There is no way it would generate enough heat to cause any issues.
I ran my ACA1220 clocked at 50MHz for 8 years, 8 hours a day. I also had stock trapdoor cover.
It was never unstable or crashed once. Unless its running at 60 -70 degs, I don't see point.
SX32, would also not throttle CPU. Its set to one speed and runs at that speed all the time.
So the heat generated will not change that much. Where as the ACA1220 could throttle cpu using a governor.
I never saw any point and just ran it as full speed all the time.