I wouldn't recommend castor oil, personally. I may have taken more than is usually given, as I took it twice. (The first time I think most of it came back up, though). I wound up with severe diarhea over the course of a few hours and that does not mix well with hemorrhoids (Sorry, TMI...).
I
did go into labor around 5 AM and had my second dd in my arms by 9:30. I'd never have done it if her heart rate had been normal, though. There was luckily no meconium issue for us.
Inflamed hemorrhoids are not a post-partum Mama's best friend. Between that and the more intense post-partum contractions that come with 2nd + births, I was pretty miserable for the first week or two post-partum.
All of that said, I would use it again as a last resort if I have reason to be concerned for my little one's health. I would start with the smallest possible dose, though ...