Originally Posted by
alan s
I use a partial frame bag, and the windage is not an issue. It's low and in the middle of the bike. Pretty much any bag will create windage, as will your body. Nothing special about the windage from a frame bag over any other bag.
Cross winds was the first thing I thought of. A trunk bag, your body, etc. I think would be a lot less of a problem than filling in that entire triangle basically completely catching all of the cross wind.