I've done this a couple of times with old water blocks. With some patience and polish the result can look even better than the original. I had to do this last week when the acrylic hold down plate included with my hfx mini cracked. Stupid acrylic, I barley touched it... I bought the thickest sheet of steel I could find on a sunday, about 1,5mm thick. I spent the better part of a day filing it down to the shape of the original hold down plate. When I mounted it it bent more than I found acceptable to so I scraped it and started from scratch. This time with a super stiff 2mm thick piece of stainless. It was a real PITA to work with this steel. It ruined my four 3mm drill bits, they barley even scratched it. So I bought new expensive drill bits which worked much better. After two solid days (three since the acrylic cracked) of drilling and filing I had new hold down and backing plates. Sadly, my struggle didn't end here. I did a test mount with some neoprene between the motherboard and the backing plate. A few hours later the computer was assembled (remember, it's a hfx case which means hours of heat pipe bending) and I fired it up. Not even a LED came on, the only life sign was the ticking sound of capacitors discharging somewhere close the the CPU... There goes the motherboard and possibly CPU I thought and went to bed. The following day I disassembled everything again and found that the neoprene had been pierced by several capacitor legs. All of them were close to the edge so I spent a few hours filing away those parts of the backing plate. This time I mounted it with a thicker sheet of neoprene and some clear plastic from an old PSU. To my surprise it booted just fine and today, about a week later, I'm writing this post on the very same computer.