I thought you remove the 3.5 inch drive. Picture:
https://eshop.macsales.com/shop/ssd/owc/imac-21.5-inch/2011 has the install video too.
More install videos out there at https://www.google.com/search?q=SSD+in+my+mid+2011+imac+21.5%22&gl=US
Putting a 3.5 SSD in my mid 2011 imac 21.5" i removed the 2.5 HHD and I'm having trouble mounting the converter bracket.
Is there anyway to attach pics, show you guys where I'm stuck?