Barri1,
Your method will be as strong or stronger than the Welsh quilting method, because the blocks will actually be attached at the edges. They should butt up tight that way. With the Welsh method, if you are a little bit too wide on the sashing, there can actually be a space between the blocks that you can feel with your fingers through the sashing. Let us know how it works out and don't stress too much this week!
Dayle