I didn't they felt plenty sturdy when I just screwed to the hardwood piece. Yours is an easy fix if they are screwed in, just glue in a piece to go to the end then put the supports back in. When I looked at that last night and compared it with the plans, I found I did NOT make a mistake I thought I had. When I received my test spool and tried to put it in, but it would not go in because of the hardwood piece. I thought I had measured something wrong and was too narrow at that spot, but couldn't figure what, everything else fit correctly. I almost cut the spool to fit, but then I thought, no I would have to do that on every spool I get. So, I filed a notch in the hardwood strip at the point. Looking at the plans I see there is a notch there! Missed it when I built the box. I feel better now.