I'm guessing the hold down in the second piece of metal in the link you provided? Not too sure why you would need that... I have my S1283 mounted using the SideWinder mount Amber recommended. It works fine for me with what they provided. All I did was break off the plastic push pins on the S1283 mounting hardware, then put the back plate on the backside of the MB and thread the spring bolts into the back plate. It's been running my E2180 cool for months.
Does that answer your question?