bptrav, I'm only just now learning the chords, not playing songs yet. But I thought it interesting that my experience with F and C7 is just like yours. And I also make that slight shift with the Barre finger otherwise my other fingers tend to lift the Barre finger up a bit when they come down. Luckily I got a great tip on C7 from someone here. Placing my pinkie and ring fingers down first and at the same time seems to have helped loads with that chord. Again, I'm no where near playing with either chord, just doing strumming/picking and slow minute changes. It's just amazing how advice on this board makes such a huge difference.