I think you're going to be pleasantly surprised when it's all said and done...and you're going to wonder why you even thought of giving this up. I think it's going to be wonderful!!!
...just wondering out loud here...what if the sashing was made of 3 narrow strips of fabric...like green on the outer sides and white or cream in the middle. (Or other colors of your choosing...) Again, I REALLY like this and I think in the end you're gonna love it! :-)