I have that cabinet for my 15-91 and you do need the swing out arm to help support the lid. I found a cart to sit next to my machine that is close to the same height for the lid and put a couple magazines on it to bring it up to be level when I open the machine since some of my quilts seem quite heavy it was just extra support. (My machine and cabinet are now 65 years old and I didn't want to trust the arm alone.)