Braap,
If the "O" rings are fresh, you shouldn't need and RTV sealant. The o ring won't melt, but they tend to go hard after a while and lose their sealing quality.
The goop that's leaking out of your header pipe isn't caused by poor sealing at the cylinder, it's caused by overly rich jetting.
Put on fresh springs and "o" rings, get your jetting right and your problems will be cured for good.