I'm really glad that you are going to add more blocks to the sides. What I've been doing lately is if I want it more for a bedspread rather than a "sleep-under" quilt, I add my borders on the sides and bottom. You already have your pillow tuck on the top, so you don't really need to add more to that.
I love your quilt. I keep thinking of doing a log cabin, but have never attempted it. And this is your first??? Wow, very impressive! Congratulations!