I've done this as well and loved it! It's been ages though
I have a fairly long foreskin... it completely covers my head and hangs a teeny bit lower. I used to be with this guy though whose foreskin hung down at least a whole inch below his head when he was soft. He could pull on it and stretch it like four inches past his head though, making a beautiful, soft sheath to hold my cock.
He had the cool ability to stay relatively soft when I was making love to his cock, allowing for maximum coverage on my penis. It always felt AMAZING doing this and cumming like this. Another foreskin is the perfect stimulation on one's cock head I think!