I've just bought a Westcott brolly to use as a shoot through; one o' them that you can take the black bit off. It came off the outer edge alright but doesn't come right off as it seems permanently attached at the crown. This surprised me as I was expecting the black outer to separate completely and I didn't want to tug too hard in case I buggered it up. Is this how it should be or is it supposed to come away entirely?