Goldsmithing cap = 11. I can\'t seem to make it on Darksday + 65% WNG moon with 68.5+2 Goldsmithing, 31.1 Smithing and 3.5 leathercraft. Leathercraft cap must be higher than 3, but probably not much. The only leathercraft item is sheep leather, which caps at 2!
From what i recall (this was years ago) I used these when skilling up well into the teens with both leather and gold getting dual skill ups. As i said, was like 5 years ago.