Encantadora- this IS usually as far as I take it, grandsire to granddaughter, though I do go back and fourth from line A to line B every other generation when appropriate.
Snickers- while I don't USUALLY do half sibling crosses, I would NOT hesitate to do so if the circumstances were right. The inbreeding coefficient is the same for half siblings as it is for grandparent to grandchild and that is 12.5%. With parent to offspring or full siblings the inbreeding coefficient is double that and much too high for my liking.
I've heard people say the same thing about breeding dogs. Breed the female back to her father. Not doing that here either, regardless of who says it's right.