I like your top, it looks very warm and inviting. I agree with duplicating what you have. Do a wider cream border and another piano border in the same width. If you still need more width, do another cream and then a scrappy binding with all the leftovers. You can make the top and bottom a bit more narrow than the sides. (These numbers are based on your strips looking like they are 2" finished.) It would work out to do a 4" cream and 4" piano on the top and bottom (do 5" on the sides) followed by a 2" cream at top and bottom (I would keep the sides at 2" or max 2 1/2") and then a binding. I believe this would still look balanced even though it is different.