Surf, good as always and backed up by experience.
I have been hearing a lot of people talking about fixed or BUIS in the upright position while shooting. Even the instructor at the carbine class I took 2 weeks ago supported this method. I have been trying to hold out for some time but will be shooting this way at this weekends class. W/ all these high level shooters doing it and the experience relayed in support of this method I would be stupid not to try it out.