If it is a client quilt I would ask. The one flannel quilt I did, I used a cotton thread with no sheen and it looked great but Glide may have as well. Sometimes color wins when it comes to thread. I will pick the color over the content or sheen.
Puddle it up on the quilt and see how it looks. I bet it will be fine. Or when you do you top baste stitch that should be a good indication of how nicely it will play with the flannel.