They're incompatible in the sense that if you breed a sharp x kahl you'll only get normals DH for sharp and kahl. No one has tried to breed them back together though. Both strains of Kahl and Sharp are recessive so if either is bred to a hypo (incomplete dominant, ie= co-dom) you'll get Hypos het for either strain and then you'd have to breed them back to get the actual sunglow.