FMQ with the back facing up

[bec]

Has anyone ever tried FMQ on the back instead of the top? I did a sample piece and noticed that the back actually looked better than the top. The top was more crinkly and places where I left more space between my design was puffy and obvious. The fabric on the back was much more smooth. I used spray to hold the sandwich together and it was smooth.

I'm also thinking that it will be harder to see where I've been on the top because of all the different prints. It is a fence rail variation so there are lots of different fabrics.

Here are pics so you can hopefully see what I'm talking about. The first one is the back of the sample. The second one is the front which doesn't show the puffiness as much as is seen in real life. The bottom one is the quilt that I'll be quilting.

Are there disadvantages to FMQing on the back?