I'm still a noob when it comes to all this stuff man, but from what I understand powdercoat gets baked in an oven to set it properly, so most fillers can't withstand the 400 degrees +, also there seems to also be some problems becuase filler doesn't conduct electricity so its harder for powder coat to stick to it. If you really want to fill and powdercoat I think you can get some fillers with metallic properties that can withstand high heats but I found it difficult to find one...
It might be easier if you just used a quality filler and get your frame sprayed with enamel...
I'm still a noob when it comes to all this stuff man, but from what I understand powdercoat gets baked in an oven to set it properly, so most fillers can't withstand the 400 degrees +, also there seems to also be some problems becuase filler doesn't conduct electricity so its harder for powder coat to stick to it. If you really want to fill and powdercoat I think you can get some fillers with metallic properties that can withstand high heats but I found it difficult to find one...
It might be easier if you just used a quality filler and get your frame sprayed with enamel...