When I think about adding different sized borders, I think it will look weird, but when I go ahead and do it, it looks fine. Don't worry, go for it!

Great idea! I make uneven widths of borders often but I prefer to make it pieced or two colours rather than one wide strip that would be 5" wide of plain fabrics. Just my personal preference.

I had a quilt that I felt needed to be longer. I added a border just on the top and bottom, where I needed to increase the dimensions. I used a material that blended with the body of the quilt. Then I added a final border around the whole quilt. It is very difficult to tell what I did or why I did it.

I have added a piano key border to the top and bottom to lengthen quilts, works out great. As said above, a great design opportunity.

Here is my Christmas quilt that started with a square, and I added uneven borders to make it a rectangle so it would fit a double bed. I say just go for it. I have also added a picture of my first machine embroidered label, it is not great, but it serves the purpose. I hope to practice more embroidery this year.

Sure you can. I have done it many times.

Absolutely. You can make a border which is a treat - a kind of floater with a fabulous focus fabric - or some clever piecing, or any number of things which will give that area a spark. Or two equal borders...A lot of opportunity to be creative

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*** Yes, it will work well, I have done it.
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Sure you can. I have done it many times.

I have done this -it really does look like it was suppose to be that way. My brother and nephews are quite tall and mattresses are extra long so adding top and bottom was the only way to go. And now my brother can make the bed without any cussing LOL