I think you will be okay. I actually do my sandwiching the same way. I do the center section and then each side section. I used to clamp stuff back down for each section, but I have quit doing that. Two-thirds of the quilt hangs down as I do each side, and I believe that is weight enough to work for me. I have had no problems doing it this way. (I just did one this way today....)
I guess you could look on the back and see if it sort of looks the same as the center section does. That might help you decide.
Dina