Mark Hennebury
When I want to get fussy with the plane i will set the throat opening as close as i can get it and still get the shaving to go through, this is in conjunction with a tight chipbreaker.
You can set both tight; the throat opening is so tight that it will hold the shaving a little tightly and you will have to tug it a little to get it out, or push it out when you take the next shaving Its also interesting to see the arrangement or the parts and to consider exactly what you mean when you are measuring the throat opening. There is a sweet spot I am sure that varies slightly between different species of woods. and for different bed angles. The sketch below is for a 45° bed BD iron with the throat edge filed to open it up for chip clearance.