Hi Wolle,

If you can find it, a 'Microfibre' filler powder is not just a 'bulk' filler and may be your best choice for this type of repair. It serve as a structural filler due to the 'loose weave' form the powder takes. Once the resin hardens, the loose weave no longer slides over each itself and forms a structure similar to OSB Board or Chip Board. It's a structure which is semi rigid and not prone to cracking when cured!

Thanks for the info, I already found the right one on Amazon.👍👍👍